Add //tools/cpp:cc_flags to the toolchains attribute.

This is so that CC_FLAGS will be resolved properly.

After the --incompatible_disable_genrule_cc_toolchain_dependency flag is
flipped, Bazel will no longer be providing CC_FLAGS to genrule by default.

PiperOrigin-RevId: 240595715
Change-Id: I067334051e89f7ec006a6b6b3d2f4188911ac2db

vdso/BUILD

@@ -55,7 +55,10 @@ genrule(
           "--check-data " +
           "--vdso $(location vdso.so) ",
     features = ["-pie"],
-    toolchains = ["@bazel_tools//tools/cpp:current_cc_toolchain"],
+    toolchains = [
+        "@bazel_tools//tools/cpp:current_cc_toolchain",
+        "@bazel_tools//tools/cpp:cc_flags",
+    ],
     tools = [
         ":check_vdso",
     ],