Remove USE_CCACHE build option

The way to use ccache has changed since this documentation & build
option were added. Update the docs with the new way to enable ccache
and remove the build option.

2 files changed, 20 insertions, 12 deletions

diff --git a/BUILD.md b/BUILD.md
index d2133cbd8..8c69cf679 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -251,7 +251,6 @@ on/off options currently supported by this repository:
 | BUILD_WSI_DIRECTFB_SUPPORT   | Linux    | `OFF`   | Build the loader with the DirectFB entry points enabled. Without this, the DirectFB headers should not be needed, but the extension `VK_EXT_directfb_surface` won't be available. |
 | BUILD_WSI_SCREEN_QNX_SUPPORT | QNX      | `OFF`   | Build the loader with the QNX Screen entry points enabled. Without this the extension `VK_QNX_screen_surface` won't be available.                                                 |
 | ENABLE_WIN10_ONECORE         | Windows  | `OFF`   | Link the loader to the [OneCore](https://msdn.microsoft.com/en-us/library/windows/desktop/mt654039.aspx) umbrella library, instead of the standard Win32 ones.                    |
-| USE_CCACHE                   | Linux    | `OFF`   | Enable caching with the CCache program.                                                                                                                                           |
 | USE_GAS                      | Linux    | `ON`    | Controls whether to build assembly files with the GNU assembler, else fallback to C code.                                                                                         |
 | USE_MASM                     | Windows  | `ON`    | Controls whether to build assembly files with MS assembler, else fallback to C code                                                                                               |
 | BUILD_STATIC_LOADER          | macOS    | `OFF`   | This allows the loader to be built as a static library on macOS. Not tested, use at your own risk.                                                                                |
@@ -265,6 +264,26 @@ The following is a table of all string options currently supported by this repos
 
 These variables should be set using the `-D` option when invoking CMake to generate the native platform files.
 
+### CCACHE
+
+There are 2 methods to enable CCACHE:
+
+1.) Set environment variables
+
+```bash
+# Requires CMake 3.17 (https://cmake.org/cmake/help/latest/envvar/CMAKE_LANG_COMPILER_LAUNCHER.html)
+export CMAKE_CXX_COMPILER_LAUNCHER=/usr/bin/ccache
+export CMAKE_C_COMPILER_LAUNCHER=/usr/bin/ccache
+```
+
+2.) Pass in cache variables
+
+```
+cmake ... -D CMAKE_CXX_COMPILER_LAUNCHER=/usr/bin/ccache -D CMAKE_C_COMPILER_LAUNCHER=/usr/bin/ccache
+```
+
+
+
 ## Building On Windows
 
 ### Windows Development Environment Requirements
@@ -481,9 +500,6 @@ You can also use
 
     cmake --build .
 
-If your build system supports ccache, you can enable that via CMake option
-`-DUSE_CCACHE=On`
-
 ### Linux Notes
 
 #### Using The Vulkan Loader Library in this Repository on Linux
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 088ed209b..90b25b6b7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -128,14 +128,6 @@ else()
     add_library(Vulkan::Headers ALIAS vulkan-headers)
 endif()
 
-option(USE_CCACHE "Use ccache" OFF)
-if(USE_CCACHE)
-    find_program(CCACHE_FOUND ccache)
-    if(CCACHE_FOUND)
-        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
-    endif()
-endif()
-
 include(GNUInstallDirs)
 
 if(UNIX AND NOT APPLE) # i.e.: Linux