Set the default --platforms value to android_arm.

This is because the default lunch target is aosp_arm.

Change-Id: I3d99f6ea99862dc2eb579be10db123fe578f9f75
Test: TH
diff --git a/android/bazel_handler.go b/android/bazel_handler.go
index 8cddbb2..63145bf 100644
--- a/android/bazel_handler.go
+++ b/android/bazel_handler.go
@@ -333,7 +333,7 @@
 	// The actual platform values here may be overridden by configuration
 	// transitions from the buildroot.
 	cmdFlags = append(cmdFlags,
-		fmt.Sprintf("--platforms=%s", "//build/bazel/platforms:android_x86_64"))
+		fmt.Sprintf("--platforms=%s", "//build/bazel/platforms:android_arm"))
 	cmdFlags = append(cmdFlags,
 		fmt.Sprintf("--extra_toolchains=%s", "//prebuilts/clang/host/linux-x86:all"))
 	// This should be parameterized on the host OS, but let's restrict to linux