MIPS: clear_cache, use _flush_cache instead of cacheflush

[wzssyqa]

Summary

The cacheflush is only defined with __USE_MISC, which depends on _DEFAULT_SOURCE, _GNU_SOURCE or _BSD_SOURCE, or _SVID_SOURCE.

If CC is called with -std=c11, these macros won't be defined, Let's use _flush_cache, which is defined always.

[brad]

Looks like this should be Ok on OpenBSD as well.

https://github.com/openbsd/src/commit/6029ab564a665c6d53d6fd049103f350efba778f

[brad]

@jrtc27 @MaskRay Ping.

compiler-rt/lib/builtins/clear_cache.c

__asm__ volatile(".set noat\n"
                      "sync\n"
                      "addiupc $at, 12\n"
                      "jr.hb $at\n"
                      "move $at, $0\n"
                      ".set at");
 #elif defined(__linux__) || defined(__OpenBSD__)
     // Pre-R6 may not be globalized. And some implementations may give strange
     // synci_step. So, let's use libc call for it.
-    cacheflush(start, end_int - start_int, BCACHE);
+    _flush_cache(start, end_int - start_int, BCACHE);
 #else
     (void)start_int;
     (void)end_int;
     compilerrt_abort();
 #endif
   }
 #elif defined(__aarch64__) && !defined(__APPLE__)
   uint64_t xstart = (uint64_t)(uintptr_t)start;