libutils_headers: export libcutils_headers

These headers are used in headers in libutils_headers and must be
re-exported.

include/utils/Atomic.h:20:#include <cutils/atomic.h>
include/utils/Trace.h:24:#include <cutils/trace.h>
include/utils/Singleton.h:27:#include <cutils/compiler.h>

Test: modules using libutils_headers don't have to have
libcutils_headers include dirs set.
Bug: 33241851

Change-Id: I039aaaad93bf0944d42f04d2a9e6654b4f867042
diff --git a/libutils/Android.bp b/libutils/Android.bp
index e912ad2..33770ba 100644
--- a/libutils/Android.bp
+++ b/libutils/Android.bp
@@ -17,8 +17,14 @@
     vendor_available: true,
     host_supported: true,
 
-    header_libs: ["libsystem_headers",],
-    export_header_lib_headers: ["libsystem_headers",],
+    header_libs: [
+        "libsystem_headers",
+        "libcutils_headers"
+    ],
+    export_header_lib_headers: [
+        "libsystem_headers",
+        "libcutils_headers"
+    ],
     export_include_dirs: ["include"],
 
     target: {