Makefile constructs

[Stefan Kost <ensonic hora-obscura de>]

hi,

I'd like to fix
https://bugzilla.gnome.org/show_bug.cgi?id=543489
  make -j for gtk-doc
https://bugzilla.gnome.org/show_bug.cgi?id=592355
  Doc generation doesn't work using "make -j3" when no DOC_MAIN_SGML_FILE exists

The second bugreport has a suggestion, but that changes the pattern used in the
gtk-doc.make makefile snippets. It is using:

#### step1 ####

step1-build.stamp: dependency1 dependency2 ...
	@echo 'gtk-doc: Building step1'
	<rules>
	@touch step1-build.stamp

step1.stamp: step1-build.stamp
	@true

#### step2 ####

step2-build.stamp: step1.stamp dependency1 dependency2 ...
	@echo 'gtk-doc: Building step2'
	...

Can anyone tell we why this is always using *two* stamps and not just

#### step1 ####

step1.stamp: dependency1 dependency2 ...
	@echo 'gtk-doc: Building step1'
	<rules>
	@touch step1.stamp

#### step2 ####

step2.stamp: step1.stamp dependency1 dependency2 ...
	@echo 'gtk-doc: Building step2'
	...


Stefan