It looks like there is a known issue:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=294729
However I'm not building a custom kernel, so the issue may have other
root causes, i.e. specific src.conf settings?. The way I build:
BUILD_DIR="/home/user/freebsd"
MACHINE=amd64
MACHINE_ARCH=amd64
FREEBSD_SRC="${BUILD_DIR:?}/src"
FREEBSD_OBJ="${BUILD_DIR:?}/obj"
# Generate src.conf
cat > ${BUILD_DIR:?}/src.conf << 'EOF'
# Enable non-default settings
WITH_BHYVE_SNAPSHOT=yes
WITH_OFED_EXTRA=yes
WITH_REPRODUCIBLE_BUILD=yes
WITH_MALLOC_PRODUCTION=yes
# Disable default settings
WITHOUT_FREEBSD_UPDATE=yes
WITHOUT_LIB32=yes
WITHOUT_TESTS=yes
WITHOUT_TESTS_SUPPORT=yes
EOF
# Build everything
env \
MAKEOBJDIRPREFIX=${FREEBSD_OBJ:?} SRCCONF="${BUILD_DIR:?}/src.conf" SYSDIR="${FREEBSD_SRC:?}/sys" \
make -C ${FREEBSD_SRC:?} TARGET=${MACHINE:?} TARGET_ARCH=${MACHINE_ARCH:?} \
-j 12 buildworld buildkernel > ${BUILD_DIR:?}/build.log 2>&1 \
|| echo "ERROR: make failed"
# Create release
env \
MAKEOBJDIRPREFIX=${FREEBSD_OBJ:?} SRCCONF="${BUILD_DIR:?}/src.conf" SYSDIR="${FREEBSD_SRC:?}/sys" \
make -C ${FREEBSD_SRC:?}/release TARGET=${MACHINE:?} TARGET_ARCH=${MACHINE_ARCH:?} \