libobjc: Add cast to void* to disable warning for casting between incompatible...

libobjc: Add cast to void* to disable warning for casting between incompatible function types [PR89586]

Even though __objc_get_forward_imp returns an IMP type, it will be casted to a compatable function
type before calling it. So we adding a cast to `void*` will disable warning about the incompatible type.

Pushed after bootstrap/test on x86_64.

libobjc/ChangeLog:

	PR libobjc/89586
	* sendmsg.c (__objc_get_forward_imp): Add cast to `void*` before casting to IMP.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>