qtbase: Fix build with musl

qtbase: Fix build with musl

This is a generic fix to accomodate musl which is adhering to posix
and doesnt have legacy to carry, so lets invert the conditional so the
special legacy case of glibc is checked and else part then covers rest
of cases which are newer glibc/uclibc and musl

(From meta-qt5 rev: d9d1d04760430cd0e5edd1764d832860715e7b83)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>