c661dbd42d injected `QT_NO_INT128` into
every TU when compiling for VxWorks.
VxWorks uses a custom stdlib implementation that does not support 128bit ints
and at the same time they use an off the shelf Clang that defines
`__SIZEOF_INT128__` which is used to detect if 128b ints are available.
This resulted in Qt falsely assuming that 128b ints are available.
Detect if 128bit are available instead of injecting `QT_NO_INT128` and
define `QT_COMPILER_SUPPORTS_INT128`, use it instead of directly
checking `__SIZEOF_INT128__`.
Task-number: QTBUG-115777
Change-Id: I7531ebe780b4bdd78b42daf8dae0e522a316a88e
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 5a10744bb4afc0c95b1b7bbba8848cf14b0bad00)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
d563ec3fba