PCRE 10.40 requires C99 now. While all GHS compiler versions we support
in Qt 6 default to C99, GHS v2016.5.4, which we use in Qt 5.15, still
defaults to C89, so set QMAKE_CFLAGS_C99 for that compiler. It doesn't
hurt in Qt 6, but enables the updated PCRE in Qt 5.15.
Pick-to: 6.3 6.2 5.15
Change-Id: I0a2d3254f80136210289a415ede7c2409b07af9b
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Kimmo Ollila <kimmo.ollila@qt.io>
a73fdd1555