title: Compiling Qt5 on MacOS with gcc-8 instead of clang
body: <p>I'm trying to compile Qt5 on MacOS, using <code>gcc-8</code> instead of the default <code>clang</code>. From this guide <a href="https://wiki.qt.io/Building_Qt_5_from_Git" rel="nofollow noreferrer">here</a> I have been able to do a configure using:</p>
  
  <pre><code>CC=gcc-8 CXX=g++-8 CFORT=gfortran-8 ../configure --prefix=/Users/qth20/Utilities/qt-5.12 -opensource -nomake examples -nomake tests -platform g++-8
  </code></pre>
  
  <p>But when I check the verbose output:</p>
  
  <pre><code>/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -c -pipe -g -fPIC -std=gnu11  -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -mmacosx-version-min=10.12 -fvisibility=hidden -w -fno-exceptions -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DPNG_ARM_NEON_OPT=0 -DPNG_POWERPC_VSX_OPT=0 -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -isystem /Users/qth20/qt5/qtbase/src/3rdparty/libpng -I. -isystem /Users/qth20/qt5/qtbase/src/3rdparty/libpng -I/Users/qth20/qt5/qtbase/mkspecs/macx-clang -o .obj/debug/pngmem.o /Users/qth20/qt5/qtbase/src/3rdparty/libpng/pngmem.c
  </code></pre>
  
  <p>It seems to be still using <code>clang</code> instead of <code>gcc-8</code>. Any suggestions to get around this?</p>