dist/Makefile: rewrite targets so they build only when sources change

Also includes a change to the top-level Makefile to accommodate new
target names.  Moved the installation variable settings close to the
install targets.

Makefile

@@ -118,12 +118,6 @@ clean: wad-image-clean
 	$(MAKE) -C lumps/textures clean
 	$(MAKE) -C bootstrap clean
 
-prefix?=/usr/local
-bindir?=/bin
-mandir?=/share/man
-waddir?=/share/games/doom
-target=$(DESTDIR)$(prefix)
-
 # Variables that are common to wad-image* targets.
 WI_LEVELS := levels
 WI_SCRIPTS := scripts
@@ -272,10 +266,16 @@ fix-map-names:
 	scripts/fix-map-names levels
 
 %.6:
-	$(MAKE) -C dist man-$*
+	$(MAKE) -C dist $@
 
 %.png:
-	$(MAKE) -C dist icon-$*
+	$(MAKE) -C dist $@
+
+prefix?=/usr/local
+bindir?=/bin
+mandir?=/share/man
+waddir?=/share/games/doom
+target=$(DESTDIR)$(prefix)
 
 install-%: $(WADS)/%.wad %.6 %.png
 	install -Dm 755 dist/freedoom "$(target)$(bindir)/$*"

dist/Makefile

@@ -1,18 +1,19 @@
-all: man-freedm man-freedoom1 man-freedoom2 \
-     icon-freedm icon-freedoom1 icon-freedoom2
+.SUFFIXES: .adoc .6
 
-man-%: freedoom.adoc
-	sed -e s/freedoom/$*/ freedoom.adoc > $*.adoc
+all: freedm.6 freedoom1.6 freedoom2.6 freedm.png freedoom1.png freedoom2.png
+
+%.6: freedoom.adoc
+	sed -e s/freedoom/$*/ $< > $*.adoc
 	a2x -f manpage $*.adoc
 
-icon-freedm:
-	./pillow-resize ../graphics/titlepic/freedm_title2.png freedm.png 64 64
+freedm.png: ../graphics/titlepic/freedm_title2.png
+	./pillow-resize $< $@ 64 64
 
-icon-freedoom1:
-	./pillow-compose ../sprites/playa2a8.png freedoom1.png 64 64
+freedoom1.png: ../sprites/playa2a8.png
+	./pillow-compose $< $@ 64 64
 
-icon-freedoom2:
-	./pillow-compose ../sprites/heada1.png freedoom2.png 64 64
+freedoom2.png: ../sprites/heada1.png
+	./pillow-compose $< $@ 64 64
 
 clean:
-	rm -f *.6 *.png freedm.adoc freedoom1.adoc freedoom2.adoc
+	$(RM) *.6 *.png freedm.adoc freedoom1.adoc freedoom2.adoc