[lldb/test] Fix libcxx configuration handling for remote platforms (llvm#172761)

When using --platform remote-* options, explicitly clear the libcxx
configuration variables instead of just warning and continuing with
potentially set values. This prevents the test suite from attempting to
use custom libcxx paths on remote platforms where they're not
applicable.

Also initialize libcxx variables to None when not specified, ensuring a
clean state regardless of how the arguments are parsed.

Signed-off-by: Med Ismail Bennani <[email protected]>
(cherry picked from commit f8377f5)

Author: medismailben

lldb/packages/Python/lldbsuite/test/dotest.py

@@ -289,15 +289,25 @@ def parseOptionsAndInitTestdirs():
             logging.warning(
                 "Custom libc++ is not supported for remote runs: ignoring --libcxx arguments"
             )
+            # Don't set libcxx paths for remote platforms - use SDK's libc++ instead
+            configuration.libcxx_include_dir = None
+            configuration.libcxx_include_target_dir = None
+            configuration.libcxx_library_dir = None
         elif not (args.libcxx_include_dir and args.libcxx_library_dir):
             logging.error(
                 "Custom libc++ requires both --libcxx-include-dir and --libcxx-library-dir"
             )
             sys.exit(-1)
         else:
+            # Use custom libcxx for local runs
             configuration.libcxx_include_dir = args.libcxx_include_dir
             configuration.libcxx_include_target_dir = args.libcxx_include_target_dir
             configuration.libcxx_library_dir = args.libcxx_library_dir
+    else:
+        # No custom libcxx specified
+        configuration.libcxx_include_dir = None
+        configuration.libcxx_include_target_dir = None
+        configuration.libcxx_library_dir = None
 
     configuration.cmake_build_type = args.cmake_build_type.lower()
 
@@ -311,7 +321,7 @@ def parseOptionsAndInitTestdirs():
         lldbtest_config.out_of_tree_debugserver = args.out_of_tree_debugserver
 
     # Set SDKROOT if we are using an Apple SDK
-    if args.sysroot is not None:
+    if args.sysroot:
         configuration.sdkroot = args.sysroot
     elif platform_system == "Darwin" and args.apple_sdk:
         configuration.sdkroot = seven.get_command_output(