add before-install.sh in travis

.travis.yml

@@ -2,10 +2,16 @@ language: cpp
 cache: ccache
 sudo: required
 dist: bionic
+
 addons:
   apt:
     update: true
+
+before_install:
+  - source ci/travis/before-install.sh
+
 install:
   - source $TRAVIS_BUILD_DIR/ci/travis/install_dependency.sh
+
 script:
   - $TRAVIS_BUILD_DIR/ci/travis/travis_build.sh

ci/travis/before-install.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -ex
+
+if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
+  export CCACHE_COMPRESS=1
+  export CCACHE_COMPRESSLEVEL=5
+  export CCACHE_COMPILERCHECK=content
+  ccache --show-stats
+fi
+
+set +ex