I'm not really familiar with imagebuilder, but it builds from source just fine - roughly following quickstart-build-images:
$ mkdir -p /tmp/pkg
$ cd /tmp/pkg
$ git clone https://git.lede-project.org/source.git
$ cd source
$ ./scripts/feeds update -a
$ ./scripts/feeds install -a
$ cat >.config <<EOF
CONFIG_TARGET_MULTI_PROFILE=y
CONFIG_TARGET_PER_DEVICE_ROOTFS=y
CONFIG_TARGET_ipq40xx=y
CONFIG_TARGET_DEVICE_ipq40xx_DEVICE_glinet_gl-b1300=y
CONFIG_TARGET_DEVICE_PACKAGES_ipq40xx_DEVICE_glinet_gl-b1300=""
CONFIG_PACKAGE_luci=y
EOF
$ make defconfig oldconfig
$ time make -j$(($(nproc) * 2))
$ du -hs bin/targets/ipq40xx/generic/*
4,0K bin/targets/ipq40xx/generic/config.seed
6,1M bin/targets/ipq40xx/generic/openwrt-ipq40xx-glinet_gl-b1300-initramfs-fit-uImage.itb
5,6M bin/targets/ipq40xx/generic/openwrt-ipq40xx-glinet_gl-b1300-squashfs-sysupgrade.bin
4,0K bin/targets/ipq40xx/generic/openwrt-ipq40xx.manifest
1,4M bin/targets/ipq40xx/generic/packages
4,0K bin/targets/ipq40xx/generic/sha256sums
(this 'needlessly' enables luci and multi-profile/ device specific rootfs', but building such a minimal set of packages shouldn't take much longer than 15-40 minutes and requires at least 10 GB free space, of course you can extend your package selection after "make defconfig oldconfig" via "make menuconfig" or "make xconfig")
What I can imagine to confuse imagebuilder though is ipq-wifi-glinet_gl-b1300 replacing parts of ath10k-firmware-qca4019 (namely /lib/firmware/ath10k/QCA4019/hw1.0/board-2.bin), while imagebuilder stumbling over this would be a bug in opkg (if opkg falls over the file duplication - or a packaging bug in ipq-wifi because of the underscore, which isn't allowed in package names), the reason for doing so will be obsolete in a couple of days PR#881.
merged just two hours ago, this issue should now be fixed, but it might take a few more hours before the snapshot/ imagebuilder binaries contain those changes.