Add RT signal to load heapprofd library.

Tests: Ran malloc_debug_unit_tests
Tests: Flashed to walleye, sent signal, observed
  "Unable to open shared library: heapprofd.so".

Change-Id: Ia8ce216837e29e3edbda8789ca28023d53fa1fda
diff --git a/libc/include/android/legacy_signal_inlines.h b/libc/include/android/legacy_signal_inlines.h
index 44c2f4f..8219759 100644
--- a/libc/include/android/legacy_signal_inlines.h
+++ b/libc/include/android/legacy_signal_inlines.h
@@ -52,7 +52,7 @@
 
 static __inline int __ndk_legacy___libc_current_sigrtmin() {
   if (__libc_current_sigrtmin) return __libc_current_sigrtmin();
-  return __SIGRTMIN + 4; /* Should match __libc_current_sigrtmin. */
+  return __SIGRTMIN + 5; /* Should match __libc_current_sigrtmin. */
 }
 
 #undef SIGRTMAX