travis: prefer TRAVIS_BUILD_DIR

Author: darwin

.travis.yml

@@ -8,7 +8,7 @@ cache:
   directories:
     - "$HOME/.m2"
     # this is mainly for puppeteer, by default it stores chromium downloads in node_modules/puppeteer/.local-chromium
-    - "$HOME/build/binaryage/cljs-devtools/test/node_modules"
+    - "$TRAVIS_BUILD_DIR/test/node_modules"
 before_install:
   - npm i -g npm
   - yes y | sudo lein upgrade