Support filtering out lit tests based on targets (llvm#1087)

Currently we ignore what targets llvm was built for in the lit tests, but recent changes to onnx-mlir explicitly initialize the available targets.
This makes the corresponding change to the lit configuration, so that we can filter out the lit tests based on the available targets.

Signed-off-by: Stella Stamenova <stilis@microsoft.com>

test/mlir/lit.cfg.py

@@ -43,3 +43,9 @@
 ]
 
 llvm_config.add_tool_substitutions(tools, tool_dirs)
+
+# This is based on the same code in llvm and it is meant to determine what
+# the supported targets for llvm & friends are - this allow us to filter test
+# execution based on the available targets
+for arch in config.targets_to_build.split():
+    config.available_features.add(arch.lower())

test/mlir/lit.site.cfg.py.in

@@ -3,6 +3,7 @@
 config.llvm_tools_dir = r"@LLVM_TOOLS_DIR@"
 config.mlir_tools_dir = r"@LLVM_TOOLS_DIR@"
 config.python_executable = "@Python3_EXECUTABLE@"
+config.targets_to_build = "@TARGETS_TO_BUILD@"
 
 config.onnx_mlir_tools_dir = r"@ONNX_MLIR_TOOLS_DIR@"
 config.onnx_mlir_obj_root = r"@ONNX_MLIR_BIN_ROOT@"