Build issue with 'make bench'

I started to see this error:

/usr/bin/gcc -std=gnu11 -O3 -fPIC -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -mcpu=power9 -DZLIB_API  -o gunzip_nx_test gunzip_nx.o ../lib/libnxz.a -lpthread
../lib/libnxz.a(nx_zlib.o):(.bss+0x4020): multiple definition of `nx_gzip_log'
gunzip_nx.o:(.bss+0x0): first defined here
../lib/libnxz.a(nx_zlib.o):(.bss+0x402c): multiple definition of `nx_dbg'
gunzip_nx.o:(.bss+0x8): first defined here
../lib/libnxz.a(nx_zlib.o): In function `sigsegv_handler':
nx_zlib.c:(.text+0x4bd0): multiple definition of `sigsegv_handler'
gunzip_nx.o:gunzip_nx.c:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:31: gunzip_nx_test] Error 1

git-bisect is pointing to the following commit:

commit 4146ff949a579f9a7ecc6daeeb564b2b8ad13bbf
Merge: be87cbb e643339
Author: Raphael Moreira Zinsly <6718397+rzinsly@users.noreply.github.com>
Date:   Thu Jun 4 09:38:09 2020 -0300

    Merge pull request #23 from rzinsly/system_tests

    Tests with page faults

libnxz / power-gzip

Build issue with 'make bench' #27