Travis: export CC during before_install stage

Signed-off-by: James Noss <jnoss@stsci.edu>

.travis.yml

@@ -153,6 +153,17 @@ matrix:
              CONDA_DEPENDENCIES=$CONDA_ALL_DEPENDENCIES
              MATPLOTLIB_VERSION=dev
 
+before_install:
+
+    # We need to use CCOMPILER otherwise Travis overwrites CC if we define it
+    # in env: above.
+    - if [ ! -z $CCOMPILER ]; then
+        export CC=$CCOMPILER;
+      fi
+
+     # Check CC variable
+    - echo $CC
+
 install:
     - git clone git://github.com/astropy/ci-helpers.git
     - source ci-helpers/travis/setup_conda.sh