Use single line per selector & don't strip license comments (#6919)

Makefile

@@ -388,8 +388,8 @@ generate-stylesheets:
 		exit 1; \
 	fi;
 	$(eval BROWSERS := "> 1%, last 2 firefox versions, last 2 safari versions, ie 11")
-	npx lessc --clean-css public/less/index.less public/css/index.css
-	$(foreach file, $(filter-out public/less/themes/_base.less, $(wildcard public/less/themes/*)),npx lessc --clean-css public/less/themes/$(notdir $(file)) > public/css/theme-$(notdir $(call strip-suffix,$(file))).css;)
+	npx lessc --clean-css="--s0 -b" public/less/index.less public/css/index.css
+	$(foreach file, $(filter-out public/less/themes/_base.less, $(wildcard public/less/themes/*)),npx lessc --clean-css="--s0 -b" public/less/themes/$(notdir $(file)) > public/css/theme-$(notdir $(call strip-suffix,$(file))).css;)
 	$(foreach file, $(wildcard public/css/*),npx postcss --use autoprefixer --autoprefixer.browsers $(BROWSERS) -o $(file) $(file);)
 
 .PHONY: swagger-ui