When comiling with ubsan, GCC is being too restrictive and ignores that
'static constexpr char []' can never be nullptr. It tries to evaluate
the comparison with nullptr, and fails with:
error: ‘(((const char*)(& hello)) == 0)’ is not a constant
Disable the checks when compiling with GCC.
Fixes: QTBUG-101307
Pick-to: 6.3 6.2
Change-Id: I8322bb7cb326e06cd03b8b107c46a494c825087b
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>