x11/xlockmore fails to build on recent poudriere jail; host and jail are at the same OS revision level:
Host:
FreeBSD 12.0-CURRENT #204 r329747: Wed Feb 21 21:06:28 CET 2018 amd64

jail:
[...]
port directory: /usr/ports/x11/xlockmore
package name: xlockmore-5.54
building for: FreeBSD pkg.walstatt.dynvpn.de 12.0-CURRENT FreeBSD 12.0-CURRENT 1200058 amd64
maintained by: jgh@FreeBSD.org
Makefile ident:      $FreeBSD: head/x11/xlockmore/Makefile 446631 2017-07-25 21:44:22Z jgh $
Poudriere version: 3.2.4
Host OSVERSION: 1200058
Jail OSVERSION: 1200058
Job Id: 03
[...]

The error is shown below.

[...]
cc -Wnested-externs -Wno-format -c  -DHAVE_CONFIG_H  -DXGLOCKRC_FILE=\"/usr/local/share/xlock/xglockrc\" -I/usr/local/include/gtk-2.0 -I/usr/local/include/pango-1.0 -I/usr/local/include/glib-2.0 -I/usr/local/lib/glib-2.0/include -I/usr/local/include -I/usr/local/include/cairo -I/usr/local/include/pixman-1 -I/usr/local/include/freetype2 -I/usr/local/include/libdrm -I/usr/local/include/libpng16 -I/usr/local/include/harfbuzz -I/usr/local/include/gdk-pixbuf-2.0 -I/usr/local/include/atk-1.0 -D_THREAD_SAFE -pthread  -I.. -I.. -O2 -pipe  -I/usr/local/include/FTGL -I/usr/local/include/freetype2 -fstack-protector -fno-strict-aliasing -pthread xglock.c
Assertion failed: (SE.DT.dominates(Ret, &*BIP)), function ReuseOrCreateCast, file /pool/sources/CURRENT/src/contrib/llvm/lib/Analysis/ScalarEvolutionExpander.cpp, line 83.
cc: error: unable to execute command: Abort trap
cc: error: clang frontend command failed due to signal (use -v to see invocation)
FreeBSD clang version 6.0.0 (branches/release_60 324090) (based on LLVM 6.0.0)
Target: x86_64-unknown-freebsd12.0
Thread model: posix
InstalledDir: /usr/bin
cc: note: diagnostic msg: PLEASE submit a bug report to https://bugs.freebsd.org/submit/ and include the crash backtrace, preprocessed source, and associated run script.
cc: note: diagnostic msg: