Move go-licenses to generate

The go-licenses check introduced in #21034 is being run on make vendor
and occassionally causes an empty go-licenses file if the vendors need to
change. This should be moved to the generate task as it is a generated file.

Ref #21034

Signed-off-by: Andrew Thornton <[email protected]>

Author: zeripath

Makefile

@@ -259,7 +259,7 @@ clean:
 fmt:
 	@MISSPELL_PACKAGE=$(MISSPELL_PACKAGE) GOFUMPT_PACKAGE=$(GOFUMPT_PACKAGE) $(GO) run build/code-batch-process.go gitea-fmt -w '{file-list}'
 	$(eval TEMPLATES := $(shell find templates -type f -name '*.tmpl'))
-	@# strip whitespace after '{{' and before `}}` unless there is only whitespace before it 
+	@# strip whitespace after '{{' and before `}}` unless there is only whitespace before it
 	@$(SED_INPLACE) -e 's/{{[ 	]\{1,\}/{{/g' -e '/^[ 	]\{1,\}}}/! s/[ 	]\{1,\}}}/}}/g' $(TEMPLATES)
 
 .PHONY: vet
@@ -398,7 +398,6 @@ unit-test-coverage:
 tidy:
 	$(eval MIN_GO_VERSION := $(shell grep -Eo '^go\s+[0-9]+\.[0-9.]+' go.mod | cut -d' ' -f2))
 	$(GO) mod tidy -compat=$(MIN_GO_VERSION)
-	@$(MAKE) --no-print-directory assets/go-licenses.json
 
 .PHONY: vendor
 vendor: tidy
@@ -709,6 +708,7 @@ backend: go-check generate $(EXECUTABLE)
 
 .PHONY: generate
 generate: $(TAGS_PREREQ)
+	@$(MAKE) --no-print-directory assets/go-licenses.json
 	@echo "Running go generate..."
 	@CC= GOOS= GOARCH= $(GO) generate -tags '$(TAGS)' $(GO_PACKAGES)