Add "isolate" argument to LOG macro to avoid TLS fetches.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index a7cc5256f5f0d4f4f55015560d90df898cc00199..03fb136e6d3945606c22b65ce82d63b6a018d681 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -143,7 +143,7 @@ void* OS::Allocate(const size_t requested,
   int prot = PROT_READ | PROT_WRITE | (is_executable ? PROT_EXEC : 0);
   void* mbase = mmap(NULL, msize, prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   if (mbase == MAP_FAILED) {
-    LOG(StringEvent("OS::Allocate", "mmap failed"));
+    LOG(ISOLATE, StringEvent("OS::Allocate", "mmap failed"));
     return NULL;
   }
   *allocated = msize;