compile qtwebengine with extra compile flag

[joeyskeys]

hi all,

I'm trying to compile qtwebengine with the flag "-D_GLIBCXX_USE_CXX11_ABI=0", it worked in qtwebengine but this flag doesn't pass along to the chromium, which will cause the inconsistency abi and then cause link stage failure.
From what i know, qtwebengine is now using gyp to generate ninja build file to build chromium, and gyp will respect the environment variable CFLAGS & CXXFLAGS, so I tried to set these environment variables in the python script gyp_qtwebengine but didn't work.
Any one know the answer to this? Please help.
BTW, is there any way to rebuild the 3rdparty packages incrementally, or it will be too time consuming to do tests.

Thanks.