[AMD][Build] Fix build issue with AMD lld (#7608)

The PR triton-lang/triton#7548 requires the use
of LLD as part of LLVM (as opposed to the system LDD), which causes the
following error when
- (1) ldd is not built, or 

- (2) the location of the `LLD_DIR` is not specified correctly:

```
      CMake Error at third_party/amd/CMakeLists.txt:6 (find_package):
        Could not find a package configuration file provided by "LLD" with any of
        the following names:
      
          LLDConfig.cmake
          lld-config.cmake
```

To fix this issue, this PR made the following changes:

- For (1), build lld in `scripts/build-llvm-project.sh`, which is
invoked by `make dev-install-llvm`. The script was added in README in
triton-lang/triton#6709, and building ldd was
added in triton-lang/triton#6049.

- For (2), make sure that `LLVM_BUILD_PATH` is an absolute path in
Makefile, so `LLD_DIR` and `MLIR_DIR` are interpereted correctly.
Otherwise CMake has hard time finding the relative location with
CMakeLists.txt in a subdirectory.
- Introduce `LLD_DIR` so we don't write `"${MLIR_DIR}/../lld"`.

Author: ShawnZhong

CMakeLists.txt

@@ -97,6 +97,10 @@ if(NOT MLIR_DIR)
   set(MLIR_DIR ${LLVM_LIBRARY_DIR}/cmake/mlir)
 endif()
 
+if(NOT LLD_DIR)
+  set(LLD_DIR ${LLVM_LIBRARY_DIR}/cmake/lld)
+endif()
+
 # MLIR
 find_package(MLIR REQUIRED CONFIG PATHS ${MLIR_DIR})
 

Makefile

@@ -6,7 +6,7 @@ PYTHON ?= python
 BUILD_DIR := $(shell cd python; $(PYTHON) -c 'from build_helpers import get_cmake_dir; print(get_cmake_dir())')
 TRITON_OPT := $(BUILD_DIR)/bin/triton-opt
 PYTEST := $(PYTHON) -m pytest
-LLVM_BUILD_PATH ?= ".llvm-project/build"
+LLVM_BUILD_PATH ?= $(realpath .llvm-project/build)
 NUM_PROCS ?= 8
 
 # Incremental builds

scripts/build-llvm-project.sh

@@ -3,7 +3,7 @@
 REPO_ROOT="$(git rev-parse --show-toplevel)"
 
 LLVM_TARGETS=${LLVM_TARGETS:-Native;NVPTX;AMDGPU}
-LLVM_PROJECTS=${LLVM_PROJECTS:-mlir;llvm}
+LLVM_PROJECTS=${LLVM_PROJECTS:-mlir;llvm;lld}
 LLVM_BUILD_TYPE=${LLVM_BUILD_TYPE:-Debug}
 LLVM_COMMIT_HASH=${LLVM_COMMIT_HASH:-$(cat "$REPO_ROOT/cmake/llvm-hash.txt")}
 LLVM_PROJECT_PATH=${LLVM_PROJECT_PATH:-"$REPO_ROOT/llvm-project"}

third_party/amd/CMakeLists.txt

@@ -3,7 +3,7 @@ include_directories(${CMAKE_CURRENT_BINARY_DIR}/include)
 add_subdirectory(include)
 add_subdirectory(lib)
 if(TRITON_BUILD_PYTHON_MODULE)
-  find_package(LLD REQUIRED CONFIG PATHS "${MLIR_DIR}/../lld" NO_DEFAULT_PATH)
+  find_package(LLD REQUIRED CONFIG PATHS "${LLD_DIR}" NO_DEFAULT_PATH)
   include_directories(${LLD_INCLUDE_DIRS})
   message(STATUS "Found LLD distro-package @ ${LLD_DIR} and LLD include dirs @ ${LLD_INCLUDE_DIRS}")
   add_triton_plugin(TritonAMD ${CMAKE_CURRENT_SOURCE_DIR}/python/triton_amd.cc LINK_LIBS TritonAMDGPUToLLVM TritonAMDGPUTransforms TritonAMDGPUDialectToLLVM)