[Sanitizers] PGO implements enable/disable SIGKILL on callers on FreeBSD

[phosek]

LGTM

compiler-rt/lib/profile/InstrProfilingUtil.c

 #include <sys/prctl.h>
 #endif
 
 #if defined(__Fuchsia__)
 #include <zircon/process.h>
 #include <zircon/syscalls.h>
 #endif
 
+#if defined(__FreeBSD__)
+#include <signal.h>
+#include <sys/procctl.h>
+#endif
+
 #include "InstrProfiling.h"
 #include "InstrProfilingUtil.h"
 
 COMPILER_RT_WEAK unsigned lprofDirMode = 0755;
 
 COMPILER_RT_VISIBILITY
 void __llvm_profile_recursive_mkdir(char *path) {
   int i;

 
 COMPILER_RT_VISIBILITY int lprofSuspendSigKill() {
 #if defined(__linux__)
   int PDeachSig = 0;
   /* Temporarily suspend getting SIGKILL upon exit of the parent process. */
   if (prctl(PR_GET_PDEATHSIG, &PDeachSig) == 0 && PDeachSig == SIGKILL)
     prctl(PR_SET_PDEATHSIG, 0);
   return (PDeachSig == SIGKILL);
+#elif defined(__FreeBSD__)
+  int PDeachSig = 0, PDisableSig = 0;
+  if (procctl(P_PID, 0, PROC_PDEATHSIG_STATUS, &PDeachSig) == 0 &&
+      PDeachSig == SIGKILL)
+    procctl(P_PID, 0, PROC_PDEATHSIG_CTL, &PDisableSig);
 #else
   return 0;
 #endif
 }
 
 COMPILER_RT_VISIBILITY void lprofRestoreSigKill() {
 #if defined(__linux__)
   prctl(PR_SET_PDEATHSIG, SIGKILL);
+#elif defined(__FreeBSD__)
+  int PEnableSig = SIGKILL;
+  procctl(P_PID, 0, PROC_PDEATHSIG_CTL, &PEnableSig);
 #endif
 }
 
 COMPILER_RT_VISIBILITY int lprofReleaseMemoryPagesToOS(uintptr_t Begin,
                                                        uintptr_t End) {
   size_t PageSize = getpagesize();
   uintptr_t BeginAligned = lprofRoundUpTo((uintptr_t)Begin, PageSize);
   uintptr_t EndAligned = lprofRoundDownTo((uintptr_t)End, PageSize);