pkg/60188: pkgsrc bootstrap fails on Linux (Slackware 15.0) due to circular dependency

>Number:         60188
>Category:       pkg
>Synopsis:       pkgsrc bootstrap fails on Linux (Slackware 15.0) due to circular dependency
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 12 14:40:00 +0000 2026
>Originator:     Daniel
>Release:        pkgsrc 2026Q1 + pkgsrc latest commit
>Organization:
>Environment:
Linux slackbook.example.org 5.15.19 #1 SMP PREEMPT Wed Feb 2 01:50:51 CST 2022 x86_64 Intel(R) Core(TM) i7-4600U CPU @ 2.10GHz GenuineIntel GNU/Linux
>Description:
When attempting to bootstrap pkgsrc on my aforementioned Linux setup, it fails with the following messages (copied with OCR, mind for typos):

===> Installing dependencies for libnbcompat-20251029
=> Tool dependency diffutils>=2.8.1: NOT found
=> Verifying reinstall for ../../devel/diffutils
=> Bootstrap dependency digest>=20211023: NOT found
=> Verifying reinstall for ../../pkgtools/digest
===> Installing dependencies for digest-20220214
=> Tool dependency mktools-[0-9]*: NOT found
=> Verifying reinstall for ../../pkgtools/mktools
===> Installing dependencies for mktools-20250213
=> Tool dependency cwrappers>=20150314: NOT found
=> Verifying reinstall for ../../pkgtools/cwrappers
===> Installing dependencies for cwrappers-20220403
=> Build dependency libnbcompat>=20221013: NOT found
=> Verifying reinstall for ../../pkgtools/libnbcompat
ERROR: [can-be-built-here.mk] This package has PKG_FAIL_REASON set:
ERROR: [bsd.pkg.mk] Circular dependency detected
*** Error code 1

This occurs with both the 2026Q1 branch and the latest pkgsrc commit.
>How-To-Repeat:
Attempt to bootstrap pkgsrc using a fresh Slackware 15.0 install
>Fix: