test: bail early if tool_path is None

tool_path will be None for llvm-go if Go cannot be found



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254190 91177308-0d34-0410-b5e6-96231b3b80d8

test/lit.cfg

@@ -236,11 +236,13 @@ def find_tool_substitution(pattern):
     tool_path = lit_config.params.get(tool_name)
     if tool_path is None:
         tool_path = lit.util.which(tool_name, llvm_tools_dir)
+        if tool_path is None:
+            return tool_name, tool_path, tool_pipe
     if (tool_name == "llc" and
        'LLVM_ENABLE_MACHINE_VERIFIER' in os.environ and
        os.environ['LLVM_ENABLE_MACHINE_VERIFIER'] == "1"):
         tool_path += " -verify-machineinstrs"
-    if (tool_name == "llvm-go" and config.go_executable is not None):
+    if (tool_name == "llvm-go"):
         tool_path += " go=" + config.go_executable
     return tool_name, tool_path, tool_pipe