Android's toolchain file, ie., android-legacy.toolchain.cmake assumes
that the default build is a Debug build, and it adds the `-g` flag to
CMAKE_<LANG>_FLAGS, as a result, our release Android build always
contains debug symbols. In this patch, I basically move the `-g` flag
from CMAKE_<LANG>_FLAGS to CMAKE_<LANG>_FLAGS_DEBUG, and
CMAKE_<LANG>_FLAGS_RELWITHDEBINFO.
Pick-to: 6.5 6.6
Fixes: QTBUG-111901
Change-Id: I31eadb07d9172c923e8beaf0ac6c6e34fe1ebefb
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
9d8a04cd1f