Building QtWebEngine: invalid directive: '%param'

[cr.zoidberg]

Trying to build QtWebEngine from current sources(followed this instructions https://wiki.qt.io/QtWebEngine_on_Windows), faced with problem where compilation breaks with this error message:

(set PATH=F:/webengine/qt5/gnuwin32/bin;%PATH:)=^)%) & win_bison --no-lines --skeleton=yacc.c --defines=glslang_tab.h --output=glslang_tab.cpp ..\..\..\3rdparty\angle\src\compiler\translator\glslang.y
..\\..\\..\\3rdparty\\angle\\src\\compiler\\translator\\glslang.y:48.1-6: error: invalid directive: '%param'
..\\..\\..\\3rdparty\\angle\\src\\compiler\\translator\\glslang.y:48.10-24: error: syntax error, unexpected {...}
NMAKE : fatal error U1077: '(set' : return code '0x1'
Stop.
NMAKE : fatal error U1077: '"C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\BIN\amd64\nmake.EXE"' : return code '0x2'
Tried to google it, with no luck. Please help!