gbuild: remove dummy rule for OUTDIR/inc

Nobody has such paths in .d files any more.

Change-Id: I0089f5ad1e69ed7a2ae7a4c33461bbeb5a47fcfd

solenv/gbuild/Package.mk

@@ -35,14 +35,6 @@ endef
 $(foreach destination,$(call gb_PackagePart_get_destinations),$(eval \
   $(call gb_PackagePart__rule,$(destination))))
 
-# Dummy rule to force rebuild of files that depend on headers in
-# $(OUTDIR)/inc (thus the dep files will be rebuild too). Otherwise
-# incremental build will fail with 'No rule to make target ...'.
-#
-# This should be removed again after some time.
-$(OUTDIR)/inc/% :
-	@true
-
 # Deliver one file to the output dir.
 #
 # gb_PackagePart_PackagePart destfile source prep-target outdir