[travis] fix paths

.travis.yml

@@ -36,7 +36,7 @@ env:
     - CCACHE_SLOPPINESS=pch_defines,time_macros
     - CCACHE_COMPRESS=1
     - CCACHE_MAXSIZE=100M
-    - PATH="/usr/lib/ccache:$PATH"
+    - PATH="/usr/lib/ccache:$HOME/gcc-symlinks:$PATH"
   matrix:
     - BACKEND=c
     - BACKEND=cpp
@@ -90,12 +90,8 @@ before_install:
   - |
     if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
       mkdir "$HOME/gcc-symlinks"
-      export PATH="$HOME/gcc-symlinks:$PATH"
-      ln -s $HOME/gcc-symlinks/gcc /usr/bin/gcc-6
-      ln -s $HOME/gcc-symlinks/g++ /usr/bin/gcc-6
-
-      which gcc
-      which g++
+      ln -s /usr/bin/gcc-6 $HOME/gcc-symlinks/gcc 
+      ln -s /usr/bin/gcc-6 $HOME/gcc-symlinks/g++ 
     fi
 
   - |