Workaround for borked sem_init library function.

src/base/platform/semaphore.cc

Index: src/base/platform/semaphore.cc
diff --git a/src/base/platform/semaphore.cc b/src/base/platform/semaphore.cc
index d5428625ba6f62231d05afe686ca65dee3b3b7c5..9e7b59a1d2cc09f16c3ef5af043fec39a67d07f1 100644
--- a/src/base/platform/semaphore.cc
+++ b/src/base/platform/semaphore.cc
@@ -75,6 +75,10 @@ bool Semaphore::WaitFor(const TimeDelta& rel_time) {
 
 Semaphore::Semaphore(int count) {
   DCHECK(count >= 0);
+#if V8_LIBC_GLIBC
+  // sem_init in glibc prior to 2.1 does not zero out semaphores.
+  memset(&native_handle_, 0, sizeof(native_handle_));
+#endif
   int result = sem_init(&native_handle_, 0, count);
   DCHECK_EQ(0, result);
   USE(result);