Two things: Fix testcase to use extern - otherwise the link will always
succeed. Also make the testcase clearer as to what we're doing and
emit a checking notification to the log.

llvm-svn: 121101
diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index b8d4a30..d186b0e 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -1325,13 +1325,21 @@
 AC_CHECK_HEADERS([CrashReporterClient.h])
 
 dnl Try to find Darwin specific crash reporting global.
-AC_LINK_IFELSE([AC_LANG_PROGRAM([[const char *__crashreporter_info__;]], [[]])],[darwin_crashreport = yes],[darwin_crashreport = no])
-AC_MSG_RESULT($darwin_crashreport)
-if test "x$darwin_crashreport = xyes"
-then
-  AC_DEFINE([HAVE_CRASHREPORTER_INFO],[1],
-            [Define if __crashreporter_info__ exists.])
-fi
+AC_MSG_CHECKING([__crashreporter_info__])
+AC_LINK_IFELSE(
+  AC_LANG_SOURCE(
+    [[extern const char *__crashreporter_info__;
+      int main() {
+        __crashreporter_info__ = "test";
+        return 0;
+      }
+    ]]),
+  AC_MSG_RESULT(yes)
+  AC_DEFINE(HAVE_CRASHREPORTER_INFO, 1, Can use __crashreporter_info__),
+  AC_MSG_RESULT(no)
+  AC_DEFINE(HAVE_CRASHREPORTER_INFO, 0,
+            Define if __crashreporter_info__ exists.))
+
 dnl===-----------------------------------------------------------------------===
 dnl===
 dnl=== SECTION 7: Check for types and structures