Changed image file to no longer be executable.

The stubs are all gone now.

Change-Id: I6eaa1bf3858759f84924a9c57c67e58bb5bb25ee
diff --git a/src/gc/space.cc b/src/gc/space.cc
index bfc3e86..1d3ee28 100644
--- a/src/gc/space.cc
+++ b/src/gc/space.cc
@@ -498,8 +498,7 @@
   }
   UniquePtr<MemMap> map(MemMap::MapFileAtAddress(image_header.GetImageBegin(),
                                                  file->GetLength(),
-                                                 // TODO: selectively PROT_EXEC stubs
-                                                 PROT_READ | PROT_WRITE | PROT_EXEC,
+                                                 PROT_READ | PROT_WRITE,
                                                  MAP_PRIVATE | MAP_FIXED,
                                                  file->Fd(),
                                                  0,