Add bionic_libc_private_headers for use by art

This avoids art having a direct reference to bionic directories which
would prevent the bionic module from being unbundled from the runtime
module.

Bug: 134379140
Test: m droid
Change-Id: I9545767b76341fd01166b675bdd156f620d4f262
diff --git a/libc/Android.bp b/libc/Android.bp
index 21ac02e..52a7aca 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1710,6 +1710,19 @@
     cmd: "$(location :bionic-generate-version-script) x86_64 $(in) $(out)",
 }
 
+// Makes bionic_tls.h available for art to use in its implementation of Thread::Current().
+cc_library_headers {
+    name: "bionic_libc_private_headers",
+    visibility: [
+        "//art:__subpackages__",
+    ],
+    host_supported: true,
+    export_include_dirs: [
+        "private",
+    ],
+    sdk_version: "current",
+}
+
 // libc_headers for libasync_safe and libpropertyinfoparser
 cc_library_headers {
     name: "libc_headers",