Fix gh-release make task on MacOS

Resolves #103

Signed-off-by: Marco Franssen <marco.franssen@philips.com>

Makefile

@@ -30,6 +30,14 @@ __check_defined = \
     $(if $(value $1),, \
       $(error Undefined $1$(if $2, ($2))))
 
+UNAME_S := $(shell uname -s)
+
+ifeq ($(UNAME_S), Darwin)
+	SED ?= gsed
+else
+	SED ?= sed
+endif
+
 .PHONY: help
 help:
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-25s\033[0m %s\n", $$1, $$2}'
@@ -109,7 +117,7 @@ gh-release: ## Creates a new release by creating a new tag and pushing it
 	@:$(call check_defined, DESCRIPTION)
 	@git stash -u
 	@echo Bumping $(OLD_VERSION) to $(NEW_VERSION)…
-	@sed -i 's/$(OLD_VERSION)/$(NEW_VERSION)/g' .github/workflows/*.yaml *.yaml *.md
+	@$(SED) -i 's/$(OLD_VERSION)/$(NEW_VERSION)/g' .github/workflows/*.yaml *.yaml *.md
 	@git add .
 	@git commit -s -m "Bump $(OLD_VERSION) to $(NEW_VERSION) for release"
 	@git tag -sam "$(DESCRIPTION)" $(NEW_VERSION)