emacs libtrivfs/file-lock.c
#include "mach_printf.h"
Add mach_printf statements.
mach_printf("libdiskfs/file-lock.c(trivfs_S_file_lock)\n");

make -C build-deb/libtrivfs
find build-deb -name 'libtrivfs.so*'
build-deb/libtrivfs/libtrivfs.so.0.3
build-deb/libtrivfs/libtrivfs.so
build-deb/lib/libtrivfs.so.0.3
srs@hurd-2014:~/hurd.debs/0.9.git20190303-1.2/libfshelp-tests$
mkdir libs
scp -p -P 5577 10.0.2.2:~/DEBs/hurd/hurd-0.9.git20190303-1.3/build-deb/libtrivfs/libtrivfs.so.0.3 libs
(cd libs; ln -s libtrivfs.so.0.3 libtrivfs.so.0)
export LD_LIBRARY_PATH=./libs
ldd /hurd/null
        libtrivfs.so.0.3 => ./libs/libtrivfs.so.0.3 (0x01029000)
./test-flock /dev/null
...
Installed version of libtrivfs.so is used not the one in libs. 
No output on console :(