p.s. I also had to rename the qtwebkit demo/examples directory (qtwebkit-examples-and-demos) before qt could be built (it couldn't find the qtwebkit headers and failed to build. On the other hand it's not a critical module so we don't really need it and can skip it).

bq. You may try computing dependencies manually by running 'make qmake' in:

didn't help

bq. or passing --makeargs="qmake" to build-webkit.

didn't help

cc1plus: warnings being treated as errors
./compiler/glslang_lex.cpp: In function ‘int yylex(YYSTYPE*, void*)’:
./compiler/glslang_lex.cpp:1713:5: error: ignoring return value of ‘size_t fwrite(const void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result

You must remove the -Werror flag from GCC or even better fix the line of code where the return value of the fwrite is not stored/evaluated. It's a macro that defines "ECHO". It should ideally be extended to evaluate the return value of fwrite and emit an error message if writing was not successfull.

As a very ugly workaround you could try something like changing:
#define ECHO fwrite( yytext, yyleng, 1, yyout )
to
#define ECHO if (fwrite( yytext, yyleng, 1, yyout )) {}