[Build] Add OpenAI triton_kernels (#28788)

Signed-off-by: Varun Sundar Rabindranath <vsundarr@redhat.com>
Co-authored-by: Varun Sundar Rabindranath <vsundarr@redhat.com>

cmake/external_projects/triton_kernels.cmake

@@ -0,0 +1,53 @@
+# Install OpenAI triton_kernels from https://github.com/triton-lang/triton/tree/main/python/triton_kernels
+
+set(DEFAULT_TRITON_KERNELS_TAG "v3.5.0")
+
+# Set TRITON_KERNELS_SRC_DIR for use with local development with vLLM. We expect TRITON_KERNELS_SRC_DIR to
+# be directly set to the triton_kernels python directory. 
+if (DEFINED ENV{TRITON_KERNELS_SRC_DIR})
+  message(STATUS "[triton_kernels] Fetch from $ENV{TRITON_KERNELS_SRC_DIR}")
+  FetchContent_Declare(
+          triton_kernels
+          SOURCE_DIR $ENV{TRITON_KERNELS_SRC_DIR}
+  )
+
+else()
+  set(TRITON_GIT "https://github.com/triton-lang/triton.git")
+  message (STATUS "[triton_kernels] Fetch from ${TRITON_GIT}:${DEFAULT_TRITON_KERNELS_TAG}")
+  FetchContent_Declare(
+          triton_kernels
+          # TODO (varun) : Fetch just the triton_kernels directory from Triton
+          GIT_REPOSITORY https://github.com/triton-lang/triton.git
+          GIT_TAG ${DEFAULT_TRITON_KERNELS_TAG}
+          GIT_PROGRESS TRUE
+          SOURCE_SUBDIR python/triton_kernels/triton_kernels
+  )
+endif()
+
+# Fetch content 
+FetchContent_MakeAvailable(triton_kernels)
+
+if (NOT triton_kernels_SOURCE_DIR)
+  message (FATAL_ERROR "[triton_kernels] Cannot resolve triton_kernels_SOURCE_DIR")
+endif()
+
+if (DEFINED ENV{TRITON_KERNELS_SRC_DIR})
+  set(TRITON_KERNELS_PYTHON_DIR "${triton_kernels_SOURCE_DIR}/")
+else()
+  set(TRITON_KERNELS_PYTHON_DIR "${triton_kernels_SOURCE_DIR}/python/triton_kernels/triton_kernels/")
+endif()
+
+message (STATUS "[triton_kernels] triton_kernels is available at ${TRITON_KERNELS_PYTHON_DIR}")
+
+add_custom_target(triton_kernels)
+
+# Ensure the vllm/third_party directory exists before installation
+install(CODE "file(MAKE_DIRECTORY \"\${CMAKE_INSTALL_PREFIX}/vllm/third_party/triton_kernels\")")
+
+## Copy .py files to install directory.
+install(DIRECTORY
+        ${TRITON_KERNELS_PYTHON_DIR}
+        DESTINATION 
+        vllm/third_party/triton_kernels/
+        COMPONENT triton_kernels
+        FILES_MATCHING PATTERN "*.py")