Reserve signal for java heap dumps.

We will put instrumentation in ART to write out Java heap memory
information on receipt of this signal.

Bug: 136210868
Test: Flash blueline-userdebug and boot

Change-Id: I63173a4051c46b8569faaf3064e1db1dbd0ea3fe
diff --git a/libc/include/android/legacy_signal_inlines.h b/libc/include/android/legacy_signal_inlines.h
index 5ca9813..d2c7677 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 + 6; /* Should match __libc_current_sigrtmin. */
+  return __SIGRTMIN + 7; /* Should match __libc_current_sigrtmin. */
 }
 
 #undef SIGRTMAX