Bug 1663613 - Add missing include directive in generated ErrorList.h. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D89432

xpcom/base/ErrorList.py

@@ -1227,6 +1227,8 @@ def error_list_h(output):
 #ifndef ErrorList_h__
 #define ErrorList_h__
 
+#include <stdint.h>
+
 """)
 
     output.write("#define NS_ERROR_MODULE_BASE_OFFSET {}\n".format(MODULE_BASE_OFFSET))