util: Fix Clang trivial destructor check.

util: Fix Clang trivial destructor check.

Check for Clang before GCC.

Clang defines __GNUC__ == 4 and __GNUC_MINOR__ == 2 and matches the GCC
check but not the GCC version for trivial destructor.

Fixes: 98ab905af0e0 ("mesa: Define introspection macro to determine
whether a type is trivially destructible.")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98526
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>