xfstests: fix depend targets

There's no need to re-make the dependency files all the time.  Make
it so the "depend" target rebuilds the ".dep" file only if necessary.
Also change the name of the dependency file created for "ltdepend"
to be ".ltdep".

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Makefile

@@ -27,8 +27,8 @@ endif
 TESTS = $(shell sed -n -e '/^[0-9][0-9][0-9]*/s/ .*//p' group)
 CONFIGURE = configure include/builddefs include/config.h
 LSRCFILES = configure configure.in aclocal.m4 README VERSION
-LDIRT = config.log .dep config.status config.cache confdefs.h conftest* \
-	check.log check.time
+LDIRT = config.log .ltdep .dep config.status config.cache confdefs.h \
+	conftest* check.log check.time
 
 ifeq ($(HAVE_DMAPI), true)
 DMAPI_MAKEFILE = dmapi/Makefile

include/buildrules

@@ -8,7 +8,7 @@ include $(TOPDIR)/include/builddefs
 
 clean clobber : $(addsuffix -clean,$(SUBDIRS))
 	$(Q)rm -f $(DIRT)
-	$(Q)rm -fr .libs .dep
+	$(Q)rm -fr .libs .ltdep .dep
 
 %-clean:
 	@echo "Cleaning $*"
@@ -75,11 +75,17 @@ $(_FORCE):
 
 MAKEDEP := $(MAKEDEPEND) $(CFLAGS)
 
-ltdepend: $(CFILES) $(HFILES)
-	@echo "    [DEP]"
-	$(Q)$(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1.lo,' > .dep
+ltdepend: .ltdep
 
-depend: $(CFILES) $(HFILES)
+.ltdep: $(CFILES) $(HFILES)
+	@echo "    [LTDEP]"
+	$(Q)[ -n "$(CFILES)" ] && \
+	    $(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1.lo,' > .ltdep
+
+depend: .dep
+
+.dep: $(CFILES) $(HFILES)
 	@echo "    [DEP]"
-	$(Q)$(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1,' > .dep
+	$(Q)[ -n "$(CFILES)" ] && \
+	    $(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1,' > .dep
 

lib/Makefile

@@ -25,4 +25,4 @@ include $(BUILDRULES)
 
 install install-dev: default
 
--include .dep
+-include .ltdep