Activate ccache for CMake

.travis.yml

@@ -26,10 +26,9 @@ env:
 
 cache:
   pip: true
+  ccache: true
   directories:
     - ${HOME}/.cache/deps
-    - ${HOME}/.ccache
-
 
 before_install:
   - source tools/test/travis-ci/functions.sh

tools/cmake/app.cmake

@@ -1,6 +1,12 @@
 # Copyright (c) 2020 ARM Limited. All rights reserved.
 # SPDX-License-Identifier: Apache-2.0
 
+find_program(CCACHE "ccache")
+if(CCACHE)
+    set(CMAKE_C_COMPILER_LAUNCHER ${CCACHE})
+    set(CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE})
+endif()
+
 include(${MBED_CONFIG_PATH}/mbed_config.cmake)
 
 # Set default toolchain file