Always use `__foo__` for attribute names.

To avoid collisions with other macros.

Change-Id: I015639043deaceccaf5f11365f8bdc45ca703da5
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 2830a49..506ab43 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -57,7 +57,7 @@
 int clearenv(void);
 
 char* _Nullable mkdtemp(char* _Nonnull __template);
-char* _Nullable mktemp(char* _Nonnull __template) __attribute__((deprecated("mktemp is unsafe, use mkstemp or tmpfile instead")));
+char* _Nullable mktemp(char* _Nonnull __template) __attribute__((__deprecated__("mktemp is unsafe, use mkstemp or tmpfile instead")));
 
 int mkostemp64(char* _Nonnull __template, int __flags) __INTRODUCED_IN(23);
 int mkostemp(char* _Nonnull __template, int __flags) __INTRODUCED_IN(23);