Revert "fix(CI/CD): correct CI variable. (go-gitea#19886)"

This reverts commit dadcaa4.

Makefile

@@ -616,27 +616,27 @@ release-windows: | $(DIST_DIRS)
 ifeq (,$(findstring gogit,$(TAGS)))
 	CGO_CFLAGS="$(CGO_CFLAGS)" $(GO) run $(XGO_PACKAGE) -go $(XGO_VERSION) -buildmode exe -dest $(DIST)/binaries -tags 'netgo osusergo gogit $(TAGS)' -ldflags '-linkmode external -extldflags "-static" $(LDFLAGS)' -targets 'windows/*' -out gitea-$(VERSION)-gogit .
 endif
-ifeq ($(CI),true)
+ifeq ($(CI),drone)
 	cp /build/* $(DIST)/binaries
 endif
 
 .PHONY: release-linux
 release-linux: | $(DIST_DIRS)
 	CGO_CFLAGS="$(CGO_CFLAGS)" $(GO) run $(XGO_PACKAGE) -go $(XGO_VERSION) -dest $(DIST)/binaries -tags 'netgo osusergo $(TAGS)' -ldflags '-linkmode external -extldflags "-static" $(LDFLAGS)' -targets '$(LINUX_ARCHS)' -out gitea-$(VERSION) .
-ifeq ($(CI),true)
+ifeq ($(CI),drone)
 	cp /build/* $(DIST)/binaries
 endif
 
 .PHONY: release-darwin
 release-darwin: | $(DIST_DIRS)
 	CGO_CFLAGS="$(CGO_CFLAGS)" $(GO) run $(XGO_PACKAGE) -go $(XGO_VERSION) -dest $(DIST)/binaries -tags 'netgo osusergo $(TAGS)' -ldflags '$(LDFLAGS)' -targets 'darwin-10.12/amd64,darwin-10.12/arm64' -out gitea-$(VERSION) .
-ifeq ($(CI),true)
+ifeq ($(CI),drone)
 	cp /build/* $(DIST)/binaries
 endif
 
 .PHONY: release-copy
 release-copy: | $(DIST_DIRS)
-	cd $(DIST); for file in `find . -type f -name "*"`; do cp $${file} ./release/; done;
+	cd $(DIST); for file in `find /build -type f -name "*"`; do cp $${file} ./release/; done;
 
 .PHONY: release-check
 release-check: | $(DIST_DIRS)