Revert "chore(build): Avoid mktemp during build, breaks opensuse pack…

…aging (#1542)"

This reverts commit c6ad2f6.

The issue on openSUSE turned out to be something else, and the mktemp
solution is just slightly more robust that the per-version filename
thing. It is less likely to reuse parts of an old test or hand generated
file in the event of weird filesystem ACLs.

Makefile.am

@@ -140,7 +140,7 @@ check: selfcheck
 
 .PHONY: selfcheck
 selfcheck: | $(_BUILT_SUBDIRS)
-	output=selfcheck-$(VERSION).pdf
+	output=$$(mktemp -t selfcheck-XXXXXX.pdf)
 	trap 'rm -f $$output' EXIT HUP TERM
 	echo "<sile>foo</sile>" | ./$(SILE) -o $$output -
 	$(PDFINFO) $$output | $(GREP) "SILE v$(VERSION)"