Replace libnativeloader-dummy-headers with libnativeloader-headers

The libnativeloader-dummy-headers target has been deprecated in favour
of the more appropriately named by otherwise identical
libnativeloader-headers

Test: m checkbuild
Change-Id: I176e0b345dea7d60d27a5fbdbcee34f7f1874088
Exempt-From-Owner-Approval: minor build change, owners unresponsive