[clang] Remove shell requirements from tests

Most of these tests do not actually have a shell requirement. The shell
requirement ended up in the test either from cargo culting (from what I
can tell) or because the test authors actually meant to mark Windows as
unsupported. This prevents enablement of lit's internal shell within
clang.

Towards #102699.

Reviewers: rnk, efriedma-quic, Sirraide, petrhosek, ilovepi

Reviewed By: ilovepi

Pull Request: llvm/llvm-project#156905

Author: boomanaiden154

lit/llvm/config.py

@@ -198,6 +198,9 @@ def __init__(self, lit_config, config):
             if gmalloc_path_str is not None:
                 self.with_environment("DYLD_INSERT_LIBRARIES", gmalloc_path_str)
 
+        if not platform.system() == "Windows":
+            features.add("symlinks")
+
     def _find_git_windows_unix_tools(self, tools_needed):
         assert sys.platform == "win32"
         import winreg