travis: export the CC/CXX variables when set

Suggested-by: Peter Wu
Fixes #4637
Closes #4640

diff --git a/.travis.yml b/.travis.yml
index 73ac0fb0181b61abee01ff1a94cbb52d110d8bea..cdfb6d6d7ab84b9f58711b896c0bd2bf1093f592 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -439,8 +439,8 @@ matrix:
                       - zlib1g-dev
 
 before_install:
-    - eval "${OVERRIDE_CC}"
-    - eval "${OVERRIDE_CXX}"
+    - export "${OVERRIDE_CC}"
+    - export "${OVERRIDE_CXX}"
 
 install:
   - if [ "$T" = "coverage" ]; then pip2 install --user cpp-coveralls; fi