[sanitizer_common] Suppress warning of cast from SignalHandlerType to sa_sigaction_t

Some buildbots have recently started complaining about "cast from 'SignalHandlerType' (aka 'void (*)(int, void *, void *)') to 'sa_sigaction_t' (aka 'void (*)(int, siginfo_t *, void *)') converts to incompatible function type [-Werror,-Wcast-function-type-strict]"
  219 |   sigact.sa_sigaction = (sa_sigaction_t)handler;
This patch does an intermediate cast to '(void (*) (void))' to suppress the warning.

N.B. SignalHandlerType has 'void*' instead of 'siginfo_t*' because it is typedef'ed in sanitizer_common/sanitizer_common.h, which does not have access to the header (signal.h) that defines siginfo_t; we therefore cannot fix SignalHandlerType.

Author: thurstond

compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp

@@ -216,7 +216,7 @@ static void MaybeInstallSigaction(int signum,
 
   struct sigaction sigact;
   internal_memset(&sigact, 0, sizeof(sigact));
-  sigact.sa_sigaction = (sa_sigaction_t)handler;
+  sigact.sa_sigaction = (sa_sigaction_t)(void (*)(void))handler;
   // Do not block the signal from being received in that signal's handler.
   // Clients are responsible for handling this correctly.
   sigact.sa_flags = SA_SIGINFO | SA_NODEFER;