Disable path mapping when rustc_env has location expansions (bazelbuild#4117)

Location expansion happens outside the control of path mapping logic and
would produce paths with build configuration in them, breaking path
mapping's logic of replacing all build configuration with the literal
"cfg".

Author: airtrick-rgb

rust/private/rustc.bzl

@@ -1446,12 +1446,17 @@ def construct_arguments(
     all_args = [process_wrapper_flags, rustc_path, rustc_flags]
     if rust_flags_args != None:
         all_args.append(rust_flags_args)
+    has_location_expansion = _has_location_expansion(authored_rustc_flags)
+    rustc_env_attr = getattr(crate_info, "rustc_env", None)
+    if not has_location_expansion and rustc_env_attr:
+        has_location_expansion = _has_location_expansion(rustc_env_attr.values())
+
     args = struct(
         process_wrapper_flags = process_wrapper_flags,
         rustc_path = rustc_path,
         rustc_flags = rustc_flags,
         extra_rustc_flags = rust_flags_args,
-        supports_path_mapping = not _has_location_expansion(authored_rustc_flags),
+        supports_path_mapping = not has_location_expansion,
         all = all_args,
     )