Use correct env for rust_test

This expands the `rust_test` environment make variables directly
instead of using the "build script" helper. The build script helper
is incorrect here and this leads issues in Bazel 8.

Author: nmattia

rust/private/rust.bzl

@@ -518,12 +518,14 @@ def _rust_test_impl(ctx):
     )
     data = getattr(ctx.attr, "data", [])
 
-    env = expand_dict_value_locations(
-        ctx,
-        getattr(ctx.attr, "env", {}),
-        data,
-        {},
-    )
+    env = {
+        key: ctx.expand_make_variables(
+            "env",
+            ctx.expand_location(value, ctx.attr.data, short_paths = True),
+            {},
+        )
+        for key, value in ctx.attr.env.items()
+    }
     if toolchain.llvm_cov and ctx.configuration.coverage_enabled:
         if not toolchain.llvm_profdata:
             fail("toolchain.llvm_profdata is required if toolchain.llvm_cov is set.")