Not all hosts are running linux...

Change-Id: I7575520b0e76bf25a19159dbbb9881bf8de792c7
diff --git a/src/common_test.h b/src/common_test.h
index dc6f3bf..7da730f 100644
--- a/src/common_test.h
+++ b/src/common_test.h
@@ -199,7 +199,13 @@
       // We need to set this so that icu4c can find its locale data.
       std::string root;
       root += getenv("ANDROID_BUILD_TOP");
+#if defined(__linux__)
       root += "/out/host/linux-x86";
+#elif defined(__APPLE__)
+      root += "/out/host/darwin-x86";
+#else
+#error unsupported OS
+#endif
       setenv("ANDROID_ROOT", root.c_str(), 1);
     }