If Qt is configured with -platform linux-g++-32 , make sure
to add the -m32 compile options for all built targets.
On 64 bit host OSes that provide both 32 and 64 bit libraries
we need to exclude the 64 bit libraries from being picked up.
The locations of the libraries are distro-specific.
This change by default excludes the Ubuntu x86_64 libraries
paths.
Opt outs are provided, which when used, forces Qt builders to
specify their own ignore paths in a custom CMake toolchain file.
The compile option and default path exclusions are added to the
Qt-generated CMake toolchain file as well, so they are reused
when building other Qt repositories.
Note that there is no foolproof way to tell CMake to ignore all
x86_64 packages / libraries, even if CMake 3.23
CMAKE_IGNORE_PREFIX_PATH is used, because there might not be
a single sysroot to exclude.
Both x86 and x86_64 libraries can co-exist in the same sysroot,
e.g in /usr
One would have to list each package / library directory in
CMAKE_IGNORE_PATH manually.
Additionally, the PKG_CONFIG_LIBDIR environment variable is also set
to Ubuntu specific prefixes, to ensure that pkg_check_modules ->
pkg-config don't pickup x86_64 libraries.
Fixes: QTBUG-101963
Change-Id: Ib17c8d2cd0ba33b2cf748772245bcd558de9120c
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
7616e4aecf