Fix travis with ccache (#6745)

.ci/travis/code_layout/install.sh

@@ -18,6 +18,6 @@ export CORES=2
 mkdir build
 pushd build
 
-cmake -DWITH_CORE=OFF -DWITH_APIDOC=ON -DWITH_ASTYLE=ON -DENABLE_TESTS=ON ..
+cmake -DUSE_CCACHE=OFF -DWITH_CORE=OFF -DWITH_APIDOC=ON -DWITH_ASTYLE=ON -DENABLE_TESTS=ON ..
 
 popd

.ci/travis/linux/docker-build-test.sh

@@ -39,6 +39,7 @@ echo "travis_fold:start:cmake"
 echo "${bold}Running cmake...${endbold}"
 cmake \
  -GNinja \
+ -DUSE_CCACHE=OFF \
  -DWITH_3D=ON \
  -DWITH_STAGED_PLUGINS=ON \
  -DWITH_GRASS=OFF \

CMakeLists.txt

@@ -29,11 +29,14 @@ SET(CMAKE_COLOR_MAKEFILE ON)
 SET(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})
 
 # Configure CCache if available
-find_program(CCACHE_FOUND ccache)
-if(CCACHE_FOUND)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
-endif(CCACHE_FOUND)
+option(USE_CCACHE "Use ccache" ON)
+if (USE_CCACHE)
+    find_program(CCACHE_FOUND ccache)
+    if(CCACHE_FOUND)
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+    endif(CCACHE_FOUND)
+endif()
 
 # in generated makefiles use relative paths so the project dir is moveable
 # Note commented out since it cause problems but it would be nice to resolve these and enable