Mark cc_library_headers targets as being bp2build_available.

Test: build/bazel/scripts/bp2build-sync.sh write.
Change-Id: I78a491d20779f50757b55c8e5305b588bf613839
diff --git a/libc/Android.bp b/libc/Android.bp
index 6ba60ca..6a3a7c0 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1823,6 +1823,7 @@
         "//apex_available:platform",
         "//apex_available:anyapex",
     ],
+    bazel_module: { bp2build_available: true },
 }
 
 cc_library_headers {
@@ -1880,6 +1881,7 @@
             export_system_include_dirs: ["kernel/uapi/asm-x86"],
         },
     },
+    bazel_module: { bp2build_available: true },
 }
 
 cc_library_headers {
@@ -1929,7 +1931,8 @@
             header_libs: ["libc_headers_arch"],
             export_header_lib_headers: ["libc_headers_arch"],
         },
-    }
+    },
+    bazel_module: { bp2build_available: true },
 }
 
 // ========================================================
diff --git a/libc/async_safe/Android.bp b/libc/async_safe/Android.bp
index 66389b9..222d9f6 100644
--- a/libc/async_safe/Android.bp
+++ b/libc/async_safe/Android.bp
@@ -47,4 +47,5 @@
         "//apex_available:platform",
         "com.android.runtime",
     ],
+    bazel_module: { bp2build_available: true },
 }