Use variables instead of file substitution in nfpm

[codefromthecrypt]

This part of the makefile could be changed to not write an intermediate file, instead temporarily setting variables like GOARCH and NFPM_VERSION

See https://github.com/goreleaser/nfpm/blob/main/www/docs/configuration.md

build/func-e_linux_%/nfpm.yaml: packaging/nfpm/nfpm.yaml build/func-e_linux_%/func-e
	@mkdir -p $(@D)
	@sed -e 's/amd64/$(*)/g' -e 's/v0.0.1/$(nfpm_version)/g' $< > $@