Patch for compiling art to run on linux target

This patch extends the build system to compile art for an aarch64
linux target.

Change-Id: If7fa10fcbb2a6e02a969f244be6e8354e36b6873
diff --git a/runtime/mem_map.cc b/runtime/mem_map.cc
index 5d89c21..771f8ed 100644
--- a/runtime/mem_map.cc
+++ b/runtime/mem_map.cc
@@ -302,8 +302,9 @@
 
   if (use_ashmem) {
     if (!kIsTargetBuild) {
-      // When not on Android ashmem is faked using files in /tmp. Ensure that such files won't
-      // fail due to ulimit restrictions. If they will then use a regular mmap.
+      // When not on Android (either host or assuming a linux target) ashmem is faked using
+      // files in /tmp. Ensure that such files won't fail due to ulimit restrictions. If they
+      // will then use a regular mmap.
       struct rlimit rlimit_fsize;
       CHECK_EQ(getrlimit(RLIMIT_FSIZE, &rlimit_fsize), 0);
       use_ashmem = (rlimit_fsize.rlim_cur == RLIM_INFINITY) ||