fixup! release: add Mac OSX installer build

Author: mjcheetham

.github/macos-installer/Makefile

@@ -21,7 +21,7 @@ GIT_PREFIX := $(PREFIX)/git
 # Replace -rc with .rc in the version string
 # This is to ensure compatibility with the format as generated by GIT-VERSION-GEN
 ORIGINAL_VERSION := $(VERSION)
-VERSION := $(shell echo $(ORIGINAL_VERSION) | sed 's/-rc/.rc/g')
+VERSION := $(subst -rc,.rc,$(VERSION))
 
 BUILD_DIR := $(GITHUB_WORKSPACE)/payload
 DESTDIR := $(PWD)/stage/git-$(ARCH_UNIV)-$(VERSION)