Fix below build with musl while here
| ../../udisks-2.1.7/udisks/udisksclient.c:2004:6: warning: '__GNUC_PREREQ' is not defined, evaluates to 0 [-Wundef]
| # if __GNUC_PREREQ(4,6) || __clang__
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>