Fix stack overflow problem in art-llvm.

For JRN54F, dex2oat needs 8MB stack size.

Change-Id: Ief8062722df9acedab2f4008b4ff149205c32c77
diff --git a/src/compiler.cc b/src/compiler.cc
index 117cc2c..2e285ce 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -1256,7 +1256,7 @@
     if (spawn_) {
       pthread_attr_t attr;
       CHECK_PTHREAD_CALL(pthread_attr_init, (&attr), "new compiler worker thread");
-      CHECK_PTHREAD_CALL(pthread_attr_setstacksize, (&attr, 4*MB), "new compiler worker thread");
+      CHECK_PTHREAD_CALL(pthread_attr_setstacksize, (&attr, 8*MB), "new compiler worker thread");
       CHECK_PTHREAD_CALL(pthread_create, (&pthread_, &attr, &Go, this), "new compiler worker thread");
       CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attr), "new compiler worker thread");
     }