[BUILD] Build with ccache by default if available (#5076)

It's a bit annoying to have to remember to pass
`TRITON_BUILD_WITH_CCACHE` every time you invoke `pip install`.

This changes the default to check if ccache is installed and use it if
it's found, with the option to manually disable ccache if it's not
wanted for some reason.

CMakeLists.txt

@@ -12,7 +12,7 @@ set(CMAKE_CXX_STANDARD 17)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
-project(triton)
+project(triton CXX)
 include(CTest)
 
 if(NOT WIN32)
@@ -26,8 +26,25 @@ option(TRITON_BUILD_TUTORIALS "Build C++ Triton tutorials" ON)
 option(TRITON_BUILD_PYTHON_MODULE "Build Python Triton bindings" OFF)
 option(TRITON_BUILD_PROTON "Build the Triton Proton profiler" ON)
 option(TRITON_BUILD_UT "Build C++ Triton Unit Tests" ON)
+option(TRITON_BUILD_WITH_CCACHE "Build with ccache (if available)" ON)
 set(TRITON_CODEGEN_BACKENDS "" CACHE STRING "Enable different codegen backends")
 
+if(TRITON_BUILD_WITH_CCACHE)
+  find_program(CCACHE_PROGRAM ccache)
+  if(CCACHE_PROGRAM)
+    set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}"
+        CACHE STRING "C compiler launcher")
+    set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}"
+        CACHE STRING "CXX compiler launcher")
+  else()
+    message(
+      STATUS
+        "Could not find ccache. Consider installing ccache to speed up compilation."
+    )
+  endif()
+endif()
+
+
 # Ensure Python3 vars are set correctly
 # used conditionally in this file and by lit tests
 

python/setup.py

@@ -460,15 +460,16 @@ def build_extension(self, ext):
                 "-DCMAKE_CXX_FLAGS=-fsanitize=address",
             ]
 
-        if check_env_flag("TRITON_BUILD_WITH_CCACHE"):
-            cmake_args += [
-                "-DCMAKE_CXX_COMPILER_LAUNCHER=ccache",
-            ]
+        # environment variables we will pass through to cmake
+        passthrough_args = [
+            "TRITON_BUILD_PROTON",
+            "TRITON_BUILD_TUTORIALS",
+            "TRITON_BUILD_WITH_CCACHE",
+        ]
+        cmake_args += [f"-D{option}={os.getenv(option)}" for option in passthrough_args if option in os.environ]
 
         if check_env_flag("TRITON_BUILD_PROTON", "ON"):  # Default ON
             cmake_args += self.get_proton_cmake_args()
-        else:
-            cmake_args += ["-DTRITON_BUILD_PROTON=OFF"]
 
         if is_offline_build():
             # unit test builds fetch googletests from GitHub