Build with "-ffile-prefix-map=$(BASEDIR)=." compiler option

Would you add this compiler option?

-ffile-prefix-map=$(BASEDIR)=.

For a host build when CFLAGS or CXXFLAGS of the environment has that option, it is used.

However for the android build it is skipped. So maybe you could always add it in that case?

This would:

• increase ccache hits (especially when using the CCACHE_BASEDIR configuration option of ccache) when building from a different basedir. See https://ccache.dev/manual/4.7.html#_compiling_in_different_directories
• maybe also increase reproducibility of the produced binaries (not sure for this one). See also https://reproducible-builds.org/docs/build-path/

I was facing many ccache misses especially in the android build because that option is not set, and the __FILE__ macro is used in the QT_REQUIRE_CONFIG macro which is defined in qtbase/src/corelib/global/qtconfigmacros.h