templatize ld.config.txt

Lists of libraries in between the linker namespaces are no longer
hard-coded in ld.config.txt, but instead come from Soong.

Bug: 37139976
Test: build 2017 pixel device with BOARD_VNDK_VERSION=current m -j
Test: the device is bootable, basic functionalities (camera, camcorder,
wifi, bt, gps, etc.) work.
Merged-In: I8170e6c3f6ee04b16359791d64cc46bd2714a073
Change-Id: I8170e6c3f6ee04b16359791d64cc46bd2714a073

(cherry picked from commit 36798460)