manta: build libmllite from source

This allows picking up a fix not to be made available yet in the
prebuilt lib used by other devices.
Needs the matching hardware/invensense/60xx/libsensors_iio/
 change Ie06912843e82811a6728cf0a67ce1cf801efa997

Bug: 18958411
Change-Id: I6ff8cf31953303075a0573466401a6b6db52eeb0
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 4e2eb7c..fe5e4fe 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -97,3 +97,5 @@
 	system_server.te
 
 MALLOC_IMPL := dlmalloc
+
+BOARD_INV_LIBMLLITE_FROM_SOURCE := true