xfstests: some refinements on "make depend"

Make it so "make depend" is a generic target, like "make clean".

Each Makefile has a "depend" target that indicates whether making
dependencies means creating ".dep" or creating ".ltdep" (or, I
suppose, both, though none do that right now).  Both files get
created even if there are no CFILES to scan (to ensure the target
up-to-date).  The "default" target now depends on "depend" (there is
no "ltdepend" any more).

Remove the "depend" and "ltdepend" definitions from the "buildrules"
file; only the actual generated files (".dep" and ".ltdep") remain
as generic targets.  The "depend' target is still defined as phony.

Do a shell trick when expanding the value of CFILES, to avoid a
problem that occurs if it is created by "make" by concatentating two
empty strings.  The problem was that in that case CFILES will
contain a space, and that wasn't getting treated as empty as
desired.

Make the rule for tool/lib dependencies more generic, to reflect the
general desire that "lib" subdirectories need to be built before
things in the "tool" subdirectories.

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

include/buildrules

@@ -6,13 +6,20 @@ _BUILDRULES_INCLUDED_ = 1
 
 include $(TOPDIR)/include/builddefs
 
+depend: $(addsuffix -depend,$(SUBDIRS))
+
+%-depend:
+	$(Q)$(MAKE) $(MAKEOPTS) -q -C $* depend || \
+	    $(MAKE) $(MAKEOPTS) -C $* depend
+
 clean clobber : $(addsuffix -clean,$(SUBDIRS))
 	$(Q)rm -f $(DIRT)
 	$(Q)rm -fr .libs .ltdep .dep
 
 %-clean:
 	@echo "Cleaning $*"
-	$(Q)$(MAKE) $(MAKEOPTS) -q -C $* clean || $(MAKE) $(MAKEOPTS) -C $* clean
+	$(Q)$(MAKE) $(MAKEOPTS) -q -C $* clean || \
+	    $(MAKE) $(MAKEOPTS) -C $* clean
 
 # Never blow away subdirs
 ifdef SUBDIRS
@@ -71,21 +78,25 @@ endif # _BUILDRULES_INCLUDED_
 $(_FORCE):
 
 # dependency build is automatic, relies on gcc -MM to generate.
-.PHONY : depend ltdepend
+.PHONY : depend
 
 MAKEDEP := $(MAKEDEPEND) $(CFLAGS)
 
-ltdepend: .ltdep
-
 .ltdep: $(CFILES) $(HFILES)
 	@echo "    [LTDEP]"
-	$(Q)[ -n "$(CFILES)" ] && \
-	    $(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1.lo,' > .ltdep
-
-depend: .dep
+	$(Q)if [ -n "$$( echo $(CFILES))" ]; then \
+	    $(MAKEDEP) $(CFILES) | \
+	    $(SED) -e 's,^\([^:]*\)\.o,\1.lo,' > .ltdep; \
+	else \
+	    cp /dev/null .ltdep; \
+	fi
 
 .dep: $(CFILES) $(HFILES)
 	@echo "    [DEP]"
-	$(Q)[ -n "$(CFILES)" ] && \
-	    $(MAKEDEP) $(CFILES) | $(SED) -e 's,^\([^:]*\)\.o,\1,' > .dep
+	$(Q)if [ -n "$$( echo $(CFILES))" ]; then \
+	    $(MAKEDEP) $(CFILES) | \
+	    $(SED) -e 's,^\([^:]*\)\.o,\1,' > .dep; \
+	else \
+	    cp /dev/null .dep; \
+	fi