.travis.yml: add ccache to speed up builds

Author: rouault

.travis.yml

@@ -6,6 +6,10 @@ php:
   - 7.1
   - 7.2
   - 7.3
+cache:
+    apt: true
+    directories:
+        - $HOME/.ccache
 
 env:
   global:
@@ -53,16 +57,18 @@ before_install:
   - sudo add-apt-repository -y ppa:ubuntugis/ppa
   - sudo add-apt-repository -y ppa:ubuntugis/ubuntugis-testing
   - sudo apt-get update
-  - sudo apt-get install --allow-unauthenticated protobuf-c-compiler libprotobuf-c0-dev bison flex python-lxml libfribidi-dev cmake librsvg2-dev colordiff libpq-dev libpng12-dev libjpeg-dev libgif-dev libgeos-dev libgd2-xpm-dev libfreetype6-dev libfcgi-dev libcurl4-gnutls-dev libcairo2-dev libgdal1-dev libproj-dev libxml2-dev python-dev libexempi-dev lcov lftp postgis libharfbuzz-dev gdal-bin
+  - sudo apt-get install --allow-unauthenticated protobuf-c-compiler libprotobuf-c0-dev bison flex python-lxml libfribidi-dev cmake librsvg2-dev colordiff libpq-dev libpng12-dev libjpeg-dev libgif-dev libgeos-dev libgd2-xpm-dev libfreetype6-dev libfcgi-dev libcurl4-gnutls-dev libcairo2-dev libgdal1-dev libproj-dev libxml2-dev python-dev libexempi-dev lcov lftp postgis libharfbuzz-dev gdal-bin ccache
   - sudo apt-get install --allow-unauthenticated libmono-system-drawing4.0-cil mono-mcs
   - sudo apt-get install --allow-unauthenticated php5-dev || sudo apt-get install --allow-unauthenticated php7-dev
   - sudo apt-get install --allow-unauthenticated libperl-dev
   - sudo pip install git+git://github.com/tbonfort/cpp-coveralls.git@extensions
-  # install swig 3.0.12 (defaults to 2.0.11 on trusty)
-  - sudo wget http://prdownloads.sourceforge.net/swig/swig-3.0.12.tar.gz
-  - tar xf swig-3.0.12.tar.gz
-  - cd swig-3.0.12 && ./configure --prefix=/usr && make && sudo make install
-  - swig -version
+  # install swig 3.0.12 (defaults to 2.0.11 on trusty)
+  - wget http://prdownloads.sourceforge.net/swig/swig-3.0.12.tar.gz
+  - export CC="ccache gcc"
+  - export CXX="ccache g++"
+  - tar xf swig-3.0.12.tar.gz
+  - cd swig-3.0.12 && ./configure --prefix=/usr && make -j2 && sudo make install
+  - swig -version
   - cd ..
   - cd msautotest
   - ./create_postgis_test_data.sh
@@ -73,7 +79,9 @@ before_install:
 
 
 script:
-  - make cmakebuild
+  - export CC="ccache gcc"
+  - export CXX="ccache g++"
+  - make cmakebuild MFLAGS="-j2"
   - make mspython-wheel
   - make -j4 test