[lldb] Transfer some environment variables into the tests on Windows build host (llvm#115613)

Some API tests (compiler calls) create a lot of garbage and cause
unexpected behavior in case of Windows host and Linux target, e.g.
```
lldb/test/API/commands/process/attach/%SystemDrive%/
lldb/test/API/functionalities/deleted-executable/%SystemDrive%/
lldb/test/API/functionalities/exec/%SystemDrive%/
lldb/test/API/functionalities/load_unload/%SystemDrive%/
lldb/test/API/functionalities/target-new-solib-notifications/%SystemDrive%/
lldb/test/API/functionalities/thread/create_after_attach/%SystemDrive%/
```
It can be fixed by transfer some standard Windows environment variables
into API tests.

Author: slydiman

lldb/test/API/lit.cfg.py

@@ -334,3 +334,9 @@ def delete_module_cache(path):
 # Propagate XDG_CACHE_HOME
 if "XDG_CACHE_HOME" in os.environ:
     config.environment["XDG_CACHE_HOME"] = os.environ["XDG_CACHE_HOME"]
+
+# Transfer some environment variables into the tests on Windows build host.
+if platform.system() == "Windows":
+    for v in ["SystemDrive"]:
+        if v in os.environ:
+            config.environment[v] = os.environ[v]