chore: run make docs with various GOOS

In order to correctly update all READMEs during go generate, pass the
primary three GOOS that we support. This way all README will get any
necessary changes.

fixes: influxdata#12499

Makefile

@@ -114,7 +114,9 @@ build_tools:
 	$(HOSTGO) build -o ./tools/readme_linter/readme_linter$(EXEEXT) ./tools/readme_linter
 
 embed_readme_%:
-	go generate -run="readme_config_includer/generator$$" ./plugins/$*/...
+	GOOS=linux go generate -run="readme_config_includer/generator$$" ./plugins/$*/...
+	GOOS=windows go generate -run="readme_config_includer/generator$$" ./plugins/$*/...
+	GOOS=darwin go generate -run="readme_config_includer/generator$$" ./plugins/$*/...
 
 .PHONY: docs
 docs: build_tools embed_readme_inputs embed_readme_outputs embed_readme_processors embed_readme_aggregators embed_readme_secretstores