makefile-fu to determine rustc output filenames given consistent and computable hashes

Makefile

RUSTC = rustc
RUSTFLAGS =

.PHONY : all
all: something

# create something's targets
$(eval $(call CRATE_LIB_TARGET, lib.rs)) 

# helper function to create crate targets for libraries
define CRATE_LIB_TARGET

INPUTS = $(1)
LIBFILE = $(firstword $(1))
PKGID = $$(shell sed -ne "s/^\#\[ *pkgid *= *\"\(.*\)\" *];$$$$/\1/p" $$(LIBFILE))
CRATE_NAME = $$(shell python -c 'import re; print re.sub("^(?:.*/)?([^\#]+).*$$$$", "\\1", "$$(PKGID)")')
CRATE_VERSION = $$(shell python -c 'import re; print re.sub("^(?:[^\#]*\#)?(.*)$$$$", "\\1", "$$(PKGID)")')
CRATE_HASH = $$(shell python -c 'import sha; print sha.new("$$(PKGID)").hexdigest()[:8]')
CRATE_OUTPUT = lib$$(CRATE_NAME)-$$(CRATE_HASH)-$$(CRATE_VERSION).dylib

.PHONY : $$(CRATE_NAME)
$$(CRATE_NAME) : $$(CRATE_OUTPUT)

$$(CRATE_OUTPUT) : $$(INPUTS)
	$$(RUSTC) $$(RUSTFLAGS) --lib $$(LIBFILE)

INPUTS =
LIBFILE =
PKGID =
CRATE_NAME =
CRATE_VERSION =
CRATE_HASH =
CRATE_OUTPUT =

endef