[compiler-rt] Move *Sanitizer:DEADLYSIGNAL printing into common part

[vitalybuka]

Summary

Part of https://github.com/google/sanitizers/issues/637

[vitalybuka]

Use posix_libcdep

compiler-rt/lib/asan/asan_posix.cc

 #include <sys/time.h>
 #include <sys/resource.h>
 #include <unistd.h>
 
 namespace __asan {
 
 void AsanOnDeadlySignal(int signo, void *siginfo, void *context) {
   ScopedDeadlySignal signal_scope(GetCurrentThread());
-  // Write the first message using fd=2, just in case.
-  // It may actually fail to write in case stderr is closed.
-  internal_write(2, SanitizerToolName, internal_strlen(SanitizerToolName));
-  static const char kDeadlySignal[] = ":DEADLYSIGNAL\n";
-  internal_write(2, kDeadlySignal, sizeof(kDeadlySignal) - 1);
+  StartReportDeadlySignal();
   SignalContext sig = SignalContext::Create(siginfo, context);
   if (IsStackOverflow(((siginfo_t *)siginfo)->si_code, sig))
     ReportStackOverflow(sig);
   else
     ReportDeadlySignal(signo, sig);
 }
 
 // ---------------------- TSD ---------------- {{{1

compiler-rt/lib/sanitizer_common/sanitizer_common.h

 // exceeded (exceeded==true) or if rss went down below the limit
 // (exceeded==false).
 // The callback should be registered once at the tool init time.
 void SetSoftRssLimitExceededCallback(void (*Callback)(bool exceeded));
 
 // Functions related to signal handling.
 typedef void (*SignalHandlerType)(int, void *, void *);
 HandleSignalMode GetHandleSignalMode(int signum);
-bool IsStackOverflow(int code, const SignalContext &sig);
 void InstallDeadlySignalHandlers(SignalHandlerType handler);
 const char *DescribeSignalOrException(int signo);
+// Signal reporting.
+void StartReportDeadlySignal();
+bool IsStackOverflow(int code, const SignalContext &sig);
 // Alternative signal stack (POSIX-only).
 void SetAlternateSignalStack();
 void UnsetAlternateSignalStack();
 
 // We don't want a summary too long.
 const int kMaxSummaryLength = 1024;
 // Construct a one-line string:
 //   SUMMARY: SanitizerToolName: error_message

compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cc

 #endif  // __powerpc__
 
   // We also check si_code to filter out SEGV caused by something else other
   // then hitting the guard page or unmapped memory, like, for example,
   // unaligned memory access.
   return IsStackAccess && (code == si_SEGV_MAPERR || code == si_SEGV_ACCERR);
 }
 
+void StartReportDeadlySignal() {
+  // Write the first message using fd=2, just in case.
+  // It may actually fail to write in case stderr is closed.
+  internal_write(2, SanitizerToolName, internal_strlen(SanitizerToolName));
+  static const char kDeadlySignal[] = ":DEADLYSIGNAL\n";
+  internal_write(2, kDeadlySignal, sizeof(kDeadlySignal) - 1);
+}
+
 #endif  // SANITIZER_GO
 
 bool IsAccessibleMemoryRange(uptr beg, uptr size) {
   uptr page_size = GetPageSizeCached();
   // Checking too large memory ranges is slow.
   CHECK_LT(size, page_size * 10);
   int sock_pair[2];
   if (pipe(sock_pair))