Add dummy description for GET-INSTALL-PATH

kati takes the first @echo command in a rule and turns it in to a ninja
description that gets pretty-printed.  The GET-INSTALL-PATH is only
@echo commands and is parsed by development/testrunner/runtest.py, so
it fails to parse the pretty-printed first test.

Add a dummy @echo to GET-INSTALL-PATH for kati to use as the
description, so the rest of the @echo commands are left unmodified.

Change-Id: I192fde48b26726a2f6760448f819243bd2f21312
diff --git a/core/main.mk b/core/main.mk
index e20128b..15b3c27 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -504,6 +504,7 @@
 # A helper goal printing out install paths
 .PHONY: GET-INSTALL-PATH
 GET-INSTALL-PATH:
+	@echo "Install paths for modules in $(ONE_SHOT_MAKEFILE):"
 	@$(foreach m, $(ALL_MODULES), $(if $(ALL_MODULES.$(m).INSTALLED), \
 		echo 'INSTALL-PATH: $(m) $(ALL_MODULES.$(m).INSTALLED)';))