It appears that since 7 August 2017 (0206c3d81e695291f17b780e77e671f95e36860b and 608f125011f3d275806598d0093526218dbfc9bf), Debian's bcftools build no longer uses /usr/lib/htslib anyway:
bcftools (1.5-1~exp1) experimental; urgency=medium [ Afif Elghraoui ] * Update packaging for new build system [snip] -- Afif Elghraoui <[email protected]> Mon, 07 Aug 2017 20:06:52 -0400 [Ignore stupid marketing footer] [University of Glasgow: The Times Scottish University of the Year 2018]
