Bug#1143323: jack-midi-clock: FTBFS: dh_auto_clean: error: make -j2 distclean returned exit code 2

Package: src:jack-midi-clock
Version: 0.4.3-2
Severity: serious
Tags: ftbfs forky sid

Dear maintainer:

During a rebuild of all packages in unstable, this package failed to build.

Below you will find the last part of the build log (probably the most
relevant part, but not necessarily). If required, the full build log
is available here:

https://people.debian.org/~sanvila/build-logs/202608/

About the archive rebuild: The build was made on virtual machines from AWS,
using sbuild and a reduced chroot with only build-essential packages.

If you cannot reproduce the bug please contact me privately, as I
am willing to provide ssh access to a virtual machine where the bug is
fully reproducible.

If this is really a bug in one of the build-depends, please use
reassign and add an affects on src:jack-midi-clock, so that this is still
visible in the BTS web page for this package.

Thanks.

--------------------------------------------------------------------------------
[...]
 debian/rules clean
dh clean
   dh_auto_clean
	make -j2 distclean
make[1]: Entering directory '/<<PKGBUILDDIR>>'
/bin/sh: 1: x86_64-linux-gnu-pkgconf: not found
Makefile:12: *** libjack from http://jackaudio.org is required
Makefile:13: *** Please install libjack-dev, libjack-jackd2-dev.  Stop.
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
dh_auto_clean: error: make -j2 distclean returned exit code 2
make: *** [debian/rules:10: clean] Error 25
dpkg-buildpackage: error: debian/rules clean subprocess failed with exit status 2
--------------------------------------------------------------------------------