Add ccache support (AcademySoftwareFoundation#1869)

Add optional support for using ccache to speed up builds.

Guarded by `MATERIALX_BUILD_USE_CCACHE` if people need to disable for some reason.

CMakeLists.txt

@@ -49,6 +49,7 @@ option(MATERIALX_BUILD_BENCHMARK_TESTS "Build benchmark tests." OFF)
 
 option(MATERIALX_BUILD_SHARED_LIBS "Build MaterialX libraries as shared rather than static." OFF)
 option(MATERIALX_BUILD_MONOLITHIC "Build a single monolithic MaterialX library." OFF)
+option(MATERIALX_BUILD_USE_CCACHE "Enable the use of ccache to speed up build time, if present." ON)
 option(MATERIALX_PYTHON_LTO "Enable link-time optimizations for MaterialX Python." ON)
 option(MATERIALX_INSTALL_PYTHON "Install the MaterialX Python package as a third-party library when the install target is built." ON)
 option(MATERIALX_INSTALL_RESOURCES "Install the resources folder when building render modules." ON)
@@ -137,6 +138,7 @@ mark_as_advanced(MATERIALX_BUILD_OIIO)
 mark_as_advanced(MATERIALX_BUILD_BENCHMARK_TESTS)
 mark_as_advanced(MATERIALX_BUILD_SHARED_LIBS)
 mark_as_advanced(MATERIALX_BUILD_MONOLITHIC)
+mark_as_advanced(MATERIALX_BUILD_USE_CCACHE)
 mark_as_advanced(MATERIALX_NAMESPACE_SUFFIX)
 mark_as_advanced(MATERIALX_LIBNAME_SUFFIX)
 mark_as_advanced(MATERIALX_PYTHON_LTO)
@@ -169,6 +171,15 @@ if (MATERIALX_BUILD_GEN_MDL)
     mark_as_advanced(MATERIALX_INSTALL_MDL_MODULE_PATH)
 endif()
 
+if (MATERIALX_BUILD_USE_CCACHE)
+    # Setup CCache for C/C++ compilation
+    find_program(CCACHE_PROGRAM ccache)
+    if(CCACHE_PROGRAM)
+        set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
+        set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}")
+    endif()
+endif()
+
 # Add global definitions
 add_definitions(-DMATERIALX_OSL_BINARY_OSLC=\"${MATERIALX_OSL_BINARY_OSLC}\")
 add_definitions(-DMATERIALX_OSL_BINARY_TESTRENDER=\"${MATERIALX_OSL_BINARY_TESTRENDER}\")