gollvm: avoid use of C headers in capture-fcn-attributes.go

Avoid use of system headers in the dummy C file used to run
through clang to capture function attributes. This helps make
the tool more useful if the cross cross compiler headers
are not available for some reason.

Updates golang/go#33711.

Change-Id: I21b72624b299571a78cbc8f1b27e7ed011b4d11f
Reviewed-on: https://go-review.googlesource.com/c/gollvm/+/190899
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/tools/capture-fcn-attributes.go b/tools/capture-fcn-attributes.go
index c3b64f4..b4cd240 100644
--- a/tools/capture-fcn-attributes.go
+++ b/tools/capture-fcn-attributes.go
@@ -67,7 +67,7 @@
 )
 
 const prog = `
-#include <inttypes.h>
+typedef unsigned long long uint64_t;
 typedef struct  {
   uint64_t a[512];
   uint64_t b[512];