tsan: use MADV_NOHUGEPAGE only if it is supported by platform

Fixes build failure on an old system:
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-centos-6.5/builds/7555/steps/build/logs/stdio

llvm-svn: 214394

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc

@@ -232,8 +232,10 @@ void InitializeShadowMemory() {
   // Frequently a thread uses only a small part of stack and similarly
   // a program uses a small part of large mmap. On some programs
   // we see 20% memory usage reduction without huge pages for this range.
+#ifdef MADV_NOHUGEPAGE
   madvise((void*)MemToShadow(0x7f0000000000ULL),
       0x10000000000ULL * kShadowMultiplier, MADV_NOHUGEPAGE);
+#endif
   DPrintf("memory shadow: %zx-%zx (%zuGB)\n",
       kLinuxShadowBeg, kLinuxShadowEnd,
       (kLinuxShadowEnd - kLinuxShadowBeg) >> 30);