cmake: Automatically include ccache if it's on the path

docs/en/get-started/linux-setup-cmake.rst

@@ -12,15 +12,15 @@ To compile with ESP-IDF you need to get the following packages:
 
 - CentOS 7::
 
-    sudo yum install git wget ncurses-devel flex bison gperf python pyserial cmake ninja-build
+    sudo yum install git wget ncurses-devel flex bison gperf python pyserial cmake ninja-build ccache
 
 - Ubuntu and Debian::
 
-    sudo apt-get install git wget libncurses-dev flex bison gperf python python-serial cmake ninja-build
+    sudo apt-get install git wget libncurses-dev flex bison gperf python python-serial cmake ninja-build ccache
 
 - Arch::
 
-    sudo pacman -S --needed gcc git make ncurses flex bison gperf python2-pyserial cmake ninja
+    sudo pacman -S --needed gcc git make ncurses flex bison gperf python2-pyserial cmake ninja ccache
 
 .. note::
     CMake version 3.5 or newer is required for use with ESP-IDF. Older Linux distributions may require updating, or enabling of a "backports" repository, or installing of a "cmake3" package not "cmake")

docs/en/get-started/macos-setup-cmake.rst

@@ -24,6 +24,8 @@ Install Prerequisites
 
   Otherwise, consult the CMake_ and Ninja_ home pages for Mac OS installation.
 
+- It is strongly recommended to also install ccache_ for faster builds. If you have HomeBrew, this can be done via ``brew install ccache``.
+
 Toolchain Setup
 ===============
 
@@ -59,3 +61,4 @@ To carry on with development environment setup, proceed to section :ref:`get-sta
 
 .. _cmake: https://cmake.org/
 .. _ninja: https://ninja-build.org/
+.. _ccache: https://ccache.samba.org/

examples/get-started/blink/CMakeLists.txt

@@ -0,0 +1,8 @@
+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.5)
+
+set(MAIN_SRCS main/blink.c)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(blink)

tools/cmake/idf_functions.cmake

@@ -86,6 +86,13 @@ function(idf_set_global_compiler_options)
 
   add_compile_options("-I${CMAKE_BINARY_DIR}") # for sdkconfig.h
 
+    # Enable ccache if it's on the path
+    find_program(CCACHE_FOUND ccache)
+    if(CCACHE_FOUND)
+        message(STATUS "ccache will be used")
+        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+    endif()
+
 endfunction(idf_set_global_compiler_options)