Add @bazel_tools//tools:bzl_srcs target

This target globs all bzl files under @bazel_tools//tools under a single filegroup.

Progress toward https://github.com/bazelbuild/bazel/issues/8859
Should fix https://github.com/bazelbuild/skydoc/issues/185 when we introduce a bzl_library target in bazel_skylib to point to this new target.

RELNOTES: None.
PiperOrigin-RevId: 266219278

tools/cpp/BUILD

diff --git a/tools/cpp/BUILD b/tools/cpp/BUILD
index d7cc616..c936d27 100644
--- a/tools/cpp/BUILD
+++ b/tools/cpp/BUILD
@@ -458,6 +458,12 @@
     srcs = ["lib_cc_configure.bzl"],
 )
 
+filegroup(
+    name = "bzl_srcs",
+    srcs = glob(["*.bzl"]),
+    visibility = ["//tools:__pkg__"],
+)
+
 load(":compiler_flag.bzl", "compiler_flag")
 
 compiler_flag(name = "compiler")