Allow building mojo_shell and non-graphical apps/services on a Mac

mojo/BUILD.gn

Index: mojo/BUILD.gn
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index ddc717695623b2a8d80fd1b2dfea30e30df5655b..281677cc95cb607dee20683754942251329587d6 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -51,7 +51,6 @@ group("tests") {
   testonly = true
   deps = [
     "//mojo/common:mojo_common_unittests",
-    "//mojo/converters/surfaces/tests:mojo_surfaces_lib_unittests",
     "//mojo/edk/system:tests",
     "//mojo/edk/test:public_tests",
     "//mojo/dart/embedder/test:dart_unittests",
@@ -63,6 +62,10 @@ group("tests") {
     "//mojo/services/files/public/c:apptests",
   ]
 
+  if (is_linux || is_android) {
+    deps += [ "//mojo/converters/surfaces/tests:mojo_surfaces_lib_unittests" ]
+  }
+
   # TODO(jamesr): We only support building V8 snapshot data on a linux host since it
   # needs a 32 bit toolchain and we don't have one configured for mac hosts.
   if (host_os == "linux") {