Use the make-target to build CSS

Less repetition, easier readable

Author: pabzm

.ci/run_browser_tests.sh

@@ -40,9 +40,7 @@ npm install
 bin/install-jsdeps.sh
 
 # Compile Elastic's styles
-npx lessc --clean-css="--s1 --advanced" skins/elastic/styles/styles.less > skins/elastic/styles/styles.min.css
-npx lessc --clean-css="--s1 --advanced" skins/elastic/styles/print.less > skins/elastic/styles/print.min.css
-npx lessc --clean-css="--s1 --advanced" skins/elastic/styles/embed.less > skins/elastic/styles/embed.min.css
+make css-elastic
 
 # Use minified javascript files
 bin/jsshrink.sh