ignore all warnings when building Qt for the Linux builds

We cannot do this for the local POSIX build as we don't know which
compiler-specific flags will disable it.

scripts/build.py

@@ -625,6 +625,8 @@ def build_mingw64_cross(config, basedir):
 
     os.chdir(build)
     if not exists('is_configured'):
+        for var in ['CFLAGS', 'CXXFLAGS']:
+            os.environ[var] = '-w'
         shell('%s/../qt/configure %s' % (basedir, configure_args))
         shell('touch is_configured')
     shell('make -j%d' % CPU_COUNT)
@@ -673,9 +675,11 @@ def build_linux_schroot(config, basedir):
     lines.append('# start of autogenerated build script')
     lines.append('cd qt_build')
     if config == 'centos5-i386':
-        lines.append('export CFLAGS=-march=i486')
-        lines.append('export CXXFLAGS=-march=i486')
-
+        lines.append('export CFLAGS="-march=i486 -w"')
+        lines.append('export CXXFLAGS="-march=i486 -w"')
+    else:
+        for var in ['CFLAGS', 'CXXFLAGS']:
+            lines.append('export %s="-w"' % var)
     lines.append('if [ ! -f is_configured ]; then')
     lines.append('  ../../../qt/configure %s || exit 1' % configure_args)
     lines.append('  touch is_configured')