Building Qt 5.15.9 with the very latest Apple clang

[BoeufBourguignon]

Hello, I'm trying to build said Qt version through conan (custom recipe) using Apple clang from Command Line Tools 15 beta 3; the exact same build with 14.2 or 14.3 was working nicely, but this compiler update broke the initial configure.

Here's the actual command line and error:

/Users/h.lacour/.conan2/p/qt9ca9d10973d5c/s/qt5/qtbase/configure -top-level -shared -confirm-license -silent -nomake examples -nomake tests -prefix /Users/h.lacour/.conan2/p/b/qt2e05e852b7af7/p -v -archdatadir /Users/h.lacour/.conan2/p/b/qt2e05e852b7af7/p/bin/archdatadir -datadir /Users/h.lacour/.conan2/p/b/qt2e05e852b7af7/p/bin/datadir -sysconfdir /Users/h.lacour/.conan2/p/b/qt2e05e852b7af7/p/bin/sysconfdir -opensource -release -skip qtdeclarative -skip qtscript -skip qtmultimedia -skip qtxmlpatterns -skip qttranslations -skip qtdoc -skip qtlocation -skip qtsensors -skip qtconnectivity -skip qtwayland -skip qt3d -skip qtimageformats -skip qtgraphicaleffects -skip qtquickcontrols -skip qtserialbus -skip qtserialport -skip qtmacextras -skip qtandroidextras -skip qtwebsockets -skip qtwebchannel -skip qtwebengine -skip qtwebview -skip qtquickcontrols2 -skip qtpurchasing -skip qtdatavis3d -skip qtvirtualkeyboard -skip qtgamepad -skip qtscxml -skip qtspeech -skip qtnetworkauth -skip qtremoteobjects -skip qtwebglplugin -skip qtlottie -skip qtquicktimeline -skip qtquick3d --zlib=system -opengl desktop -no-vulkan -openssl-runtime --glib=no --pcre=system --fontconfig=no --icu=no --sql-mysql=yes --sql-psql=yes --sql-odbc=yes --zstd=yes -no-dbus -no-feature-gssapi -system-doubleconversion -system-freetype -no-harfbuzz -system-libjpeg -system-libpng -system-sqlite -system-libmd4c ZLIB_LIBS=-lz OPENSSL_LIBS=-lssl -lcrypto PCRE2_LIBS=-lpcre2-32 -lpcre2-16 -lpcre2-posix -lpcre2-8 -lz -lbz2 DOUBLECONVERSION_LIBS=-ldouble-conversion FREETYPE_INCDIR=/Users/h.lacour/.conan2/p/b/freetc1591c0a6670c/p/include/freetype2 FREETYPE_LIBS=-lfreetype -lpng -lz -lbz2 -lbrotlienc-static -lbrotlidec-static -lbrotlicommon-static LIBJPEG_LIBS=-ljpeg LIBPNG_LIBS=-lpng -lz SQLITE_LIBS=-lsqlite3 MYSQL_LIBS=-lmysqlclient -lc++ -lssl -lcrypto -lz -lzstd -llz4 PSQL_LIBS=-lpq -lpgcommon -lpgcommon_shlib -lpgport -lpgport_shlib ODBC_LIBS=-lodbccr -lodbcinst -lodbc -lltdl -liconv -lcharset ZSTD_LIBS=-lzstd LIBMD4C_LIBS=-lmd4c-html -lmd4c -I /Users/h.lacour/.conan2/p/b/pcre20c8f79f2d448b/p/include -D PCRE2_STATIC -I /Users/h.lacour/.conan2/p/b/doubl358f4fd009642/p/include -I /Users/h.lacour/.conan2/p/b/freetc1591c0a6670c/p/include -I /Users/h.lacour/.conan2/p/b/freetc1591c0a6670c/p/include/freetype2 -I /Users/h.lacour/.conan2/p/b/libjp1451c0fd25428/p/include -D LIBJPEG_STATIC -I /Users/h.lacour/.conan2/p/b/libpn5288b5bcda671/p/include -I /Users/h.lacour/.conan2/p/b/sqlitaaf641ce3caab/p/include -I /Users/h.lacour/.conan2/p/b/libmy1124e691c5d4a/p/include -I /Users/h.lacour/.conan2/p/b/opens2a358758324b1/p/include -I /Users/h.lacour/.conan2/p/b/zlib5b2a01f60dc7f/p/include -I /Users/h.lacour/.conan2/p/b/libpqfa83bdf7dfe4f/p/include -I /Users/h.lacour/.conan2/p/b/odbc5ac1f48094897/p/include -D GL_SILENCE_DEPRECATION=1 -I /Users/h.lacour/.conan2/p/b/zstd4cf189ca3039b/p/include -I /Users/h.lacour/.conan2/p/b/md4cd1bb73c3d0dfc/p/include QMAKE_LIBDIR+=/Users/h.lacour/.conan2/p/b/pcre20c8f79f2d448b/p/lib /Users/h.lacour/.conan2/p/b/doubl358f4fd009642/p/lib /Users/h.lacour/.conan2/p/b/freetc1591c0a6670c/p/lib /Users/h.lacour/.conan2/p/b/bzip21fb642867a96c/p/lib /Users/h.lacour/.conan2/p/b/brotled8776de5cf01/p/lib /Users/h.lacour/.conan2/p/b/libjp1451c0fd25428/p/lib /Users/h.lacour/.conan2/p/b/libpn5288b5bcda671/p/lib /Users/h.lacour/.conan2/p/b/sqlitaaf641ce3caab/p/lib /Users/h.lacour/.conan2/p/b/libmy1124e691c5d4a/p/lib /Users/h.lacour/.conan2/p/b/opens2a358758324b1/p/lib /Users/h.lacour/.conan2/p/b/zlib5b2a01f60dc7f/p/lib /Users/h.lacour/.conan2/p/b/lz448b62dfe3af20/p/lib /Users/h.lacour/.conan2/p/b/libpqfa83bdf7dfe4f/p/lib /Users/h.lacour/.conan2/p/b/odbc5ac1f48094897/p/lib /Users/h.lacour/.conan2/p/b/libto6bcdfec4924cb/p/lib /Users/h.lacour/.conan2/p/b/libicf411cd1c43918/p/lib /Users/h.lacour/.conan2/p/b/zstd4cf189ca3039b/p/lib /Users/h.lacour/.conan2/p/b/md4cd1bb73c3d0dfc/p/lib QMAKE_RPATHLINKDIR+=/Users/h.lacour/.conan2/p/b/pcre20c8f79f2d448b/p/lib:/Users/h.lacour/.conan2/p/b/doubl358f4fd009642/p/lib:/Users/h.lacour/.conan2/p/b/freetc1591c0a6670c/p/lib:/Users/h.lacour/.conan2/p/b/bzip21fb642867a96c/p/lib:/Users/h.lacour/.conan2/p/b/brotled8776de5cf01/p/lib:/Users/h.lacour/.conan2/p/b/libjp1451c0fd25428/p/lib:/Users/h.lacour/.conan2/p/b/libpn5288b5bcda671/p/lib:/Users/h.lacour/.conan2/p/b/sqlitaaf641ce3caab/p/lib:/Users/h.lacour/.conan2/p/b/libmy1124e691c5d4a/p/lib:/Users/h.lacour/.conan2/p/b/opens2a358758324b1/p/lib:/Users/h.lacour/.conan2/p/b/zlib5b2a01f60dc7f/p/lib:/Users/h.lacour/.conan2/p/b/lz448b62dfe3af20/p/lib:/Users/h.lacour/.conan2/p/b/libpqfa83bdf7dfe4f/p/lib:/Users/h.lacour/.conan2/p/b/odbc5ac1f48094897/p/lib:/Users/h.lacour/.conan2/p/b/libto6bcdfec4924cb/p/lib:/Users/h.lacour/.conan2/p/b/libicf411cd1c43918/p/lib:/Users/h.lacour/.conan2/p/b/zstd4cf189ca3039b/p/lib:/Users/h.lacour/.conan2/p/b/md4cd1bb73c3d0dfc/p/lib -mysql_config /Users/h.lacour/.conan2/p/b/libmy1124e691c5d4a/p/bin/mysql_config -psql_config /Users/h.lacour/.conan2/p/b/libpqfa83bdf7dfe4f/p/bin/pg_config -no-framework QMAKE_APPLE_DEVICE_ARCHS=arm64 -platform macx-clang
Performing shadow build...
Preparing build tree...
Creating qmake...
Info: creating cache file /Users/h.lacour/.conan2/p/b/qt2e05e852b7af7/b/build_folder/.qmake.cache
Command line: ...
Project ERROR: failed to parse default search paths from compiler output

and here's the .qmake.stash file produced:

QMAKE_MAC_SDK.macosx.Path = /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
QMAKE_MAC_SDK.macosx.SDKVersion = 14.0
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_CC = /Library/Developer/CommandLineTools/usr/bin/clang
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_CXX = /Library/Developer/CommandLineTools/usr/bin/clang++
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_FIX_RPATH = \
    /Library/Developer/CommandLineTools/usr/bin/install_name_tool \
    -id
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_AR = \
    /Library/Developer/CommandLineTools/usr/bin/ar \
    cq
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_RANLIB = \
    /Library/Developer/CommandLineTools/usr/bin/ranlib \
    -s
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_LINK = /Library/Developer/CommandLineTools/usr/bin/clang++
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_LINK_SHLIB = /Library/Developer/CommandLineTools/usr/bin/clang++
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_LINK_C = /Library/Developer/CommandLineTools/usr/bin/clang
QMAKE_MAC_SDK.macx-clang.macosx.QMAKE_LINK_C_SHLIB = /Library/Developer/CommandLineTools/usr/bin/clang
QMAKE_CXX.QT_COMPILER_STDCXX = 199711L
QMAKE_CXX.QMAKE_APPLE_CC = 6000
QMAKE_CXX.QMAKE_APPLE_CLANG_MAJOR_VERSION = 15
QMAKE_CXX.QMAKE_APPLE_CLANG_MINOR_VERSION = 0
QMAKE_CXX.QMAKE_APPLE_CLANG_PATCH_VERSION = 0
QMAKE_CXX.QMAKE_GCC_MAJOR_VERSION = 4
QMAKE_CXX.QMAKE_GCC_MINOR_VERSION = 2
QMAKE_CXX.QMAKE_GCC_PATCH_VERSION = 1
QMAKE_CXX.COMPILER_MACROS = \
    QT_COMPILER_STDCXX \
    QMAKE_APPLE_CC \
    QMAKE_APPLE_CLANG_MAJOR_VERSION \
    QMAKE_APPLE_CLANG_MINOR_VERSION \
    QMAKE_APPLE_CLANG_PATCH_VERSION \
    QMAKE_GCC_MAJOR_VERSION \
    QMAKE_GCC_MINOR_VERSION \
    QMAKE_GCC_PATCH_VERSION

So, I don't expect a saviour to help me out of this predicament, but I'd like to get an idea about the meaning and reason of this error. Does Qt have some hardcoded info about compilers being tripped by the latest clang? Is there a way to debug this issue any further?