Fix LLVM build with host gcc 13

Building LLVM with a host gcc 13 fails and suggests including <cstdint>
in external/apache2/llvm/dist/llvm/include/llvm/Support/Signals.h .
Instead of this, joerg@ suggested not modifying the llvm vendor branch
but instead working around this in our LLVM build infrastructure.

external/apache2/llvm/autoconf/include/llvm/Config/config.h.in

@@ -3,6 +3,10 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+#ifdef __cplusplus
+#include <cstdint>
+#endif
+
 /* Exported configuration */
 #include "llvm/Config/llvm-config.h"
 

tools/llvm-lib/libLLVMSupport/Makefile

@@ -1,3 +1,5 @@
-#	$NetBSD: Makefile,v 1.1 2011/02/06 01:14:16 joerg Exp $
+#	$NetBSD: Makefile,v 1.2 2023/05/30 19:05:05 hgutch Exp $
+
+CPPFLAGS.Signals.cpp+=	-include llvm/Config/config.h
 
 .include <bsd.init.mk>