third_party: Include libutil in sysroot.

This is necessary for linking the `process_wrapper` from `rules_rust`.

third_party/debian_stretch_amd64_sysroot.BUILD

diff --git a/third_party/debian_stretch_amd64_sysroot.BUILD b/third_party/debian_stretch_amd64_sysroot.BUILD
index 1898176..3dd94fa 100644
--- a/third_party/debian_stretch_amd64_sysroot.BUILD
+++ b/third_party/debian_stretch_amd64_sysroot.BUILD
@@ -134,6 +134,20 @@
 )
 
 cc_toolchain_import(
+    name = "util",
+    additional_libs = [
+        "lib/x86_64-linux-gnu/libutil-2.24.so",
+        "lib/x86_64-linux-gnu/libutil.so.1",
+    ],
+    shared_library = "usr/lib/x86_64-linux-gnu/libutil.so",
+    static_library = "usr/lib/x86_64-linux-gnu/libutil.a",
+    target_compatible_with = select({
+        "@platforms//os:linux": ["@platforms//cpu:x86_64"],
+        "//conditions:default": ["@platforms//:incompatible"],
+    }),
+)
+
+cc_toolchain_import(
     name = "libc",
     hdrs = glob([inc + "/**/*.h" for inc in INCLUDES] + [inc + "/*.h" for inc in INCLUDES]),
     additional_libs = [
@@ -154,6 +168,7 @@
         ":gcc",
         ":math",
         ":mvec",
+        ":util",
         "@rules_cc_toolchain_config//:compiler_rt",
     ],
 )