Fix a SIGSTKFLT typo.

Stupid Unix guys. A few extra letters here and there wouldn't have killed them,
and it would have made a lot of things a lot more readable.

Change-Id: I0cb5f7eeef0ecaf7d1bd819f1b72af6393708edd
diff --git a/src/runtime_linux.cc b/src/runtime_linux.cc
index 75540b8..e2c806d 100644
--- a/src/runtime_linux.cc
+++ b/src/runtime_linux.cc
@@ -118,7 +118,7 @@
     case SIGILL: return "SIGILL";
     case SIGPIPE: return "SIGPIPE";
     case SIGSEGV: return "SIGSEGV";
-#if defined(STIGSTLFKT)
+#if defined(SIGSTKFLT)
     case SIGSTKFLT: return "SIGSTKFLT";
 #endif
     case SIGTRAP: return "SIGTRAP";