Mark targets as PHONY modules

This does not really change anything, but is necessary for some extra
checks I'm implementing in the build system.

Test: add --writable=out/ to kati flags, see fewer warnings after this change
Change-Id: Iaa2034512b39c8d146b89665df667a85bf5f2e1b
diff --git a/Android.mk b/Android.mk
index 4040a1c..adf3524 100644
--- a/Android.mk
+++ b/Android.mk
@@ -29,6 +29,7 @@
 	@rm -f $(HOST_OUT)/acts-dist/acts.zip
 	$(hide) zip -r $(HOST_OUT)/acts-dist/acts.zip tools/test/connectivity/acts/*
 acts: $(ACTS_DISTRO)
+.PHONY: acts
 
 $(call dist-for-goals,tests,$(ACTS_DISTRO))
 
@@ -53,6 +54,7 @@
 	$(hide) chmod 755 $(WTS_ACTS_DISTRO)
 
 wts-acts: $(WTS_ACTS_DISTRO)
+.PHONY: wts-acts
 
 $(call dist-for-goals,tests,$(WTS_ACTS_DISTRO))