[make] [lib/version] remove a misplaced .PHONY (#170)

When lib/version was included, a rule depended on .PHONY.  This would
unexpectedly invoke other rules defined as dependent on .PHONY (standard
phony-ness signal).

As a side effect, this used to generate srcfiles.txt and
include_paths.txt in build dir. Since they are useful, we might always
build those anyway, and not make them phony at all.

make/build.mk

@@ -54,13 +54,9 @@ $(BUILDDIR)/srcfiles.txt:
 	@echo generating $@
 	$(NOECHO)echo $(sort $(ALLSRCS)) | tr ' ' '\n' > $@
 
-.PHONY: $(BUILDDIR)/srcfiles.txt
-
 $(BUILDDIR)/include_paths.txt:
 	@echo generating $@
 	$(NOECHO)echo $(subst -I,,$(sort $(GLOBAL_INCLUDES))) | tr ' ' '\n' > $@
 
-.PHONY: $(BUILDDIR)/include_paths.txt
-
 #include arch/$(ARCH)/compile.mk