thinrope:

With current HEAD (403260d), build with my configuration fails consistently due to missing directory.

I do make distclean; cp /tmp/.config .config; make oldconfig; make
Here is the relevant portion (upon make -j1 V=s):
...
make[3]: Leaving directory '/srv/OpenWRT/openwrt/openwrt/package/utils/bzip2'
make[3]: Entering directory '/srv/OpenWRT/openwrt/openwrt/package/utils/e2fsprogs'
install -d -m0755 /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/share/et
cp -fpR /srv/OpenWRT/openwrt/openwrt/build_dir/hostpkg/e2fsprogs-1.43.7/lib/et/et_[ch].awk /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/share/et/
install -d -m0755 /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/share/ss
cp -fpR /srv/OpenWRT/openwrt/openwrt/build_dir/hostpkg/e2fsprogs-1.43.7/lib/ss/ct_c.{sed,awk} /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/share/ss/
install -d -m0755 /srv/OpenWRT/openwrt/openwrt/staging_dir/host/bin
cp -fpR /srv/OpenWRT/openwrt/openwrt/build_dir/hostpkg/e2fsprogs-1.43.7/lib/et/compile_et /srv/OpenWRT/openwrt/openwrt/build_dir/hostpkg/e2fsprogs-1.43.7/lib/ss/mk_cmds /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/bin/
cp: target '/srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/bin/' is not a directory
make[3]: *** [Makefile:318: /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/stamp/.e2fsprogs_installed] Error 1
make[3]: Leaving directory '/srv/OpenWRT/openwrt/openwrt/package/utils/e2fsprogs'
make[2]: *** [package/Makefile:107: package/utils/e2fsprogs/host/compile] Error 2
make[2]: Leaving directory '/srv/OpenWRT/openwrt/openwrt'
make[1]: *** [package/Makefile:103: /srv/OpenWRT/openwrt/openwrt/staging_dir/target-mips_24kc_musl/stamp/.package_compile] Error 2
make[1]: Leaving directory '/srv/OpenWRT/openwrt/openwrt'
make: *** [/srv/OpenWRT/openwrt/openwrt/include/toplevel.mk:218: world] Error 2

mkdir /srv/OpenWRT/openwrt/openwrt/staging_dir/hostpkg/bin/ fixes the problem, until later make distclean
I am not sure where is this directory made, but it fails, even with -j1, so probably not a concurrency issue.

I am attaching my .config, although it probably is not specific to my case.