If a vendor (or vendor_available) lib has a dependency to a llndk
library, the name of the llndk library is modified to <name>.llndk.
There was a bug that this name modification is done only for shared_libs
property, but not for export_shared_lib_headers property. As a result,
the headers of the llndk was not re-exported. Fix the bug by modifying
export_shared_lib_headers property as well.
Bug: 63178444
Test: build
Test: look into out/soong/Android-<target>.mk. libutils.vendor has
system/core/liblog/include_vndk in its LOCAL_EXPORT_CFLAGS.
Change-Id: I6fcb1036cdb81ba167ead815b436a5cada283ede