[WIP] [halium-7.1] main.mk: include halium/biometryd

[konradybcio]

Without this ninja won't pick up the directory

Change-Id: I453dc369760f82b009ba2191cc8f702c4cc65bd5

[Herrie82]

@konradybcio Are you sure you PR-ed this against the correct branch? In order for it to pick up biometryd it should exist as well and therefore be pulled in by https://github.com/Halium/android/blob/halium-7.1/default.xml which it's not doing currently it seems?

[konradybcio]

I only made the PR as a preparation for that. Biometryd still needs some love on Nougat before we can ship it by default.

[Herrie82]

@konradybcio OK I will keep it pending for now then. Please link to this PR when you put the necessary bits in place elsewhere.