Merge pull request #35528 from 3405691582/OpenBSDSwiftStdint54

[5.4][stdlib] Use Clang type macros on OpenBSD.

Author: tkremenek

stdlib/public/SwiftShims/SwiftStdint.h

@@ -24,7 +24,7 @@
 
 // Clang has been defining __INTxx_TYPE__ macros for a long time.
 // __UINTxx_TYPE__ are defined only since Clang 3.5.
-#if !defined(__APPLE__) && !defined(__linux__)
+#if !defined(__APPLE__) && !defined(__linux__) && !defined(__OpenBSD__)
 #include <stdint.h>
 typedef int64_t __swift_int64_t;
 typedef uint64_t __swift_uint64_t;