Fix clang warning / miscompile

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6271005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72364 0039d316-1c4b-4281-b951-d872f2087c98

breakpad/linux/generate-test-dump.cc

@@ -57,7 +57,7 @@ static bool DumpCallback(const char* dump_path, const char* minidump_id,
 
 static void DoSomethingWhichCrashes() {
   int local_var = 1;
-  *reinterpret_cast<char*>(NULL) = 1;
+  *reinterpret_cast<volatile char*>(NULL) = 1;
 }
 
 int main() {