fix(build): add step to Makefile to generate signing gpg key

Signed-off-by: Cheng Fang <[email protected]>

Makefile

@@ -124,7 +124,8 @@ release-binaries:
 	BINNAME=argocd-image-updater-win64.exe OUTDIR=dist/release OS=windows ARCH=amd64 make controller
 	rm -f dist/release/release-v${VERSION}.sha256 dist/release/release-v${VERSION}.sha256.asc
 	for bin in dist/release/argocd-image-updater-*; do sha256sum "$$bin" >> dist/release/release-v${VERSION}.sha256; done
-	gpg -a --detach-sign dist/release/release-v${VERSION}.sha256
+	gpg --batch --generate-key hack/gpg-key.conf
+	gpg --default-key [email protected] -a --detach-sign dist/release/release-v${VERSION}.sha256
 	gpg -a --verify dist/release/release-v${VERSION}.sha256.asc
 
 .PHONY: extract-binary

hack/gpg-key.conf

@@ -0,0 +1,13 @@
+%no-protection
+%echo Generating a standard key
+Key-Type: RSA
+Key-Length: 3072
+Subkey-Type: RSA
+Subkey-Length: 3072
+Name-Real: argocd-image-updater
+Name-Comment: signing key
+Name-Email: [email protected]
+Expire-Date: 1
+%commit
+%echo done
+