Add compatibility with GCC <= 11.2

GCC versions prior to 11.3 do not support the "mwait" target attribute.
This change adds compiler version checks to the pragmas using this
attribute, enabling builds with GCC 11.1 & 11.2.

Signed-off-by: Andrei Tatar <andrei@unikraft.io>
Reviewed-by: Stefan Jumarea <stefanjumarea02@gmail.com>
Reviewed-by: Maria Sfiraiala <maria.sfiraiala@gmail.com>
Reviewed-by: Radu Nichita <radunichita99@gmail.com>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #4

include-gcc/mwaitintrin.h

@@ -24,11 +24,13 @@
 #ifndef _MWAITINTRIN_H_INCLUDED
 #define _MWAITINTRIN_H_INCLUDED
 
+#if ((__GNUC__ >= 12) || (__GNUC__ == 11 && __GNUC_MINOR__ >= 3))
 #ifndef __MWAIT__
 #pragma GCC push_options
 #pragma GCC target("mwait")
 #define __DISABLE_MWAIT__
 #endif /* __MWAIT__ */
+#endif /* GCC >= 11.3 */
 
 extern __inline void
 __attribute__((__gnu_inline__, __always_inline__, __artificial__))