mediaex: Fix build rule under Make

Ninja automatically creates the output directory for a rule, but make
does not. Add mkdir -p so that make builds work.

Change-Id: I123226b2b1b641d268ad0a4922172d43506741cf
diff --git a/services/mediaextractor/minijail/Android.mk b/services/mediaextractor/minijail/Android.mk
index 5e03918..79c5505 100644
--- a/services/mediaextractor/minijail/Android.mk
+++ b/services/mediaextractor/minijail/Android.mk
@@ -22,6 +22,7 @@
 include $(BUILD_SYSTEM)/base_rules.mk
 
 $(LOCAL_BUILT_MODULE): $(LOCAL_SRC_FILES)
-	cat > $@ $^
+	@mkdir -p $(dir $@)
+	$(hide) cat > $@ $^
 
 endif