rules_rust_deduplicate_sysroot.diff

diff --git a/rust/private/rustc.bzl b/rust/private/rustc.bzl
index eff542eb39..ad682f359e 100644
--- a/rust/private/rustc.bzl
+++ b/rust/private/rustc.bzl
@@ -1059,7 +1059,8 @@ def construct_arguments(
         ))

     # Ensure the sysroot is set for the target platform
-    env["SYSROOT"] = toolchain.sysroot
+    if not toolchain._incompatible_no_rustc_sysroot_env:
+        env["SYSROOT"] = toolchain.sysroot
     if toolchain._experimental_toolchain_generated_sysroot:
         rustc_flags.add(toolchain.sysroot, format = "--sysroot=%s")

diff --git a/rust/settings/BUILD.bazel b/rust/settings/BUILD.bazel
index 1f23709fb7..faaa1489c0 100644
--- a/rust/settings/BUILD.bazel
+++ b/rust/settings/BUILD.bazel
@@ -98,3 +98,10 @@ incompatible_flag(
     build_setting_default = True,
     issue = "https://github.com/bazelbuild/rules_rust/issues/2324",
 )
+
+# A flag to remove the SYSROOT environment variable from `Rustc` actions.
+incompatible_flag(
+    name = "incompatible_no_rustc_sysroot_env",
+    build_setting_default = True,
+    issue = "https://github.com/bazelbuild/rules_rust/issues/2429",
+)
diff --git a/rust/toolchain.bzl b/rust/toolchain.bzl
index a9b2e1f5af..9580d7cfc4 100644
--- a/rust/toolchain.bzl
+++ b/rust/toolchain.bzl
@@ -643,6 +643,7 @@ def _rust_toolchain_impl(ctx):
         _experimental_use_global_allocator = experimental_use_global_allocator,
         _experimental_use_coverage_metadata_files = ctx.attr._experimental_use_coverage_metadata_files[BuildSettingInfo].value,
         _experimental_toolchain_generated_sysroot = ctx.attr._experimental_toolchain_generated_sysroot[IncompatibleFlagInfo].enabled,
+        _incompatible_no_rustc_sysroot_env = ctx.attr._incompatible_no_rustc_sysroot_env[IncompatibleFlagInfo].enabled,
         _incompatible_test_attr_crate_and_srcs_mutually_exclusive = ctx.attr._incompatible_test_attr_crate_and_srcs_mutually_exclusive[IncompatibleFlagInfo].enabled,
         _no_std = no_std,
     )
@@ -807,6 +808,9 @@ rust_toolchain = rule(
                 "This flag is only relevant when used together with --@rules_rust//rust/settings:experimental_use_global_allocator."
             ),
         ),
+        "_incompatible_no_rustc_sysroot_env": attr.label(
+            default = Label("//rust/settings:incompatible_no_rustc_sysroot_env"),
+        ),
         "_incompatible_test_attr_crate_and_srcs_mutually_exclusive": attr.label(
             default = Label("//rust/settings:incompatible_test_attr_crate_and_srcs_mutually_exclusive"),
         ),