ci: speed up code-coverage jobs

refs #3809

Change-Id: If8c5284d5e21d5a30e543ea070fde3d1f199d771
diff --git a/.travis.yml b/.travis.yml
index 1066eb7..49058cc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,8 @@
 sudo: required
 language: generic
+env:
+  global:
+    - JOB_NAME=limited-build
 matrix:
   include:
     - os: linux