mk: Fix warnings about duplicated rules

The footer.tex rule didn't depend on $(1) of the macro it was being defined in,
so it was getting duplicated, causing many warnings.

Author: alexcrichton

mk/docs.mk

@@ -147,6 +147,10 @@ SHOULD_BUILD_PDF_DOC_$(1) = 1
 endef
 $(foreach docname,$(PDF_DOCS),$(eval $(call DEF_SHOULD_BUILD_PDF_DOC,$(docname))))
 
+doc/footer.tex: $(D)/footer.inc | doc/
+	@$$(call E, pandoc: $$@)
+	$$(CFG_PANDOC) --from=html --to=latex $$< --output=$$@
+
 define DEF_DOC
 
 # HTML (rustdoc)
@@ -163,10 +167,6 @@ doc/$(1).epub: $$(D)/$(1).md | doc/
 	@$$(call E, pandoc: $$@)
 	$$(CFG_PANDOC) $$(PANDOC_EPUB_OPTS) $$< --output=$$@
 
-doc/footer.tex: $(D)/footer.inc | doc/
-	@$$(call E, pandoc: $$@)
-	$$(CFG_PANDOC) --from=html --to=latex $$< --output=$$@
-
 # PDF (md =(pandoc)=> tex =(pdflatex)=> pdf)
 DOC_TARGETS += doc/$(1).tex
 doc/$(1).tex: $$(D)/$(1).md doc/footer.tex doc/version.tex | doc/