Add some friendly messages to libcxx calls to abort().

llvm-svn: 186951
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 1468d0cec7676c4ed2a1982d05a640317eed13cd
diff --git a/src/string.cpp b/src/string.cpp
index c6fe408..daed7d2 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -16,6 +16,7 @@
 #ifdef _WIN32
 #include "support/win32/support.h"
 #endif // _WIN32
+#include <stdio.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -38,6 +39,7 @@
 #ifndef _LIBCPP_NO_EXCEPTIONS
     throw T( msg );
 #else
+    printf("%s\n", msg.c_str());
     abort();
 #endif
 }