Include mlir_tools_dir in the PATH used in test environment,
as otherwise mlir-reduce is unable to find mlir-opt when building
standalone (and hence mlir_tools_dir != llvm_tools_dir).
Differential Revision: https://reviews.llvm.org/D110992
config.test_exec_root = os.path.join(config.mlir_obj_root, 'test')
# Tweak the PATH to include the tools dir.
+llvm_config.with_environment('PATH', config.mlir_tools_dir, append_path=True)
llvm_config.with_environment('PATH', config.llvm_tools_dir, append_path=True)
tool_dirs = [config.mlir_tools_dir, config.llvm_tools_dir]