build+make: move release script

Because this script is now run from the main Makefile, it is more
suitable to be located in the main scripts folder where the other
build related scripts reside.

Makefile

@@ -129,7 +129,7 @@ install:
 release:
 	@$(call print, "Releasing lnd and lncli binaries.")
 	$(VERSION_CHECK)
-	./build/release/release.sh build-release "$(VERSION_TAG)" "$(BUILD_SYSTEM)" "$(RELEASE_TAGS)" "$(RELEASE_LDFLAGS)"
+	./scripts/release.sh build-release "$(VERSION_TAG)" "$(BUILD_SYSTEM)" "$(RELEASE_TAGS)" "$(RELEASE_LDFLAGS)"
 
 scratch: build