Revert "jenkins: use ccache with devtoolset on ppc64le"

This reverts commit 70df2a4.

It breaks node-test-commit-v8-linux:
- #1940

Author: sam-github

jenkins/scripts/select-compiler.sh

@@ -27,9 +27,6 @@ if [ "$SELECT_ARCH" = "PPC64LE" ]; then
       if [ "$NODEJS_MAJOR_VERSION" -gt "9" ]; then
         # Setup devtoolset-6, sets LD_LIBRARY_PATH, PATH, etc.
         . /opt/rh/devtoolset-6/enable
-        export CC="ccache ppc64le-redhat-linux-gcc"
-        export CXX="ccache ppc64le-redhat-linux-g++"
-        export LINK="ppc64le-redhat-linux-g++"
         echo "Compiler set to devtoolset-6"
 	return
       fi