libhardware: export system headers

libhardware uses system headers in its headers.

Test: links
Test: libraries using libhardware which don't have access to system
headers link when BOARD_VNDK_VERSION := current.
Bug: 33241851
(cherry picked from commit d39335254a55089a37ac63c2764dfe7efd292ec4)
Merged-In: I33cbd8a4d6188eed69cb8b55acb3b78b0628d82a
Change-Id: I33cbd8a4d6188eed69cb8b55acb3b78b0628d82a
diff --git a/Android.bp b/Android.bp
index 739cb6d..f3426e8 100644
--- a/Android.bp
+++ b/Android.bp
@@ -2,6 +2,9 @@
 
 cc_library_headers {
     name: "libhardware_headers",
+    header_libs: ["libsystem_headers"],
+    export_header_lib_headers: ["libsystem_headers"],
+
     export_include_dirs: ["include"],
     vendor_available: true,
 }
@@ -15,9 +18,11 @@
         "liblog",
         "libdl",
     ],
-    header_libs: ["libsystem_headers"],
     cflags: ["-DQEMU_HARDWARE"],
-    export_include_dirs: ["include"],
+
+    header_libs: ["libhardware_headers"],
+    export_header_lib_headers: ["libhardware_headers"],
+
     vendor_available: true,
 }