OS build for generic-x86-64 fails ~every second time

[agners]

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Around 50% of builds the OS build fails during grub2 package build:

2022-07-13T08:39:10.7131593Z /build/output/host/bin/x86_64-buildroot-linux-gnu-gcc -E -DHAVE_CONFIG_H -I. -I..  -Wall -W -DGRUB_UTIL=1 -D_FILE_OFFSET_BITS=64 -I./include -DGRUB_FILE=\"util/grub-fstest.c\" -I. -I.. -I. -I.. -I../include -I./include -I../grub-core/lib/libgcrypt-grub/src/ -I./grub-core/lib/gnulib -I../grub-core/lib/gnulib  -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -fno-stack-protector -D_FILE_OFFSET_BITS=64 \
2022-07-13T08:39:10.7132965Z   -D'GRUB_MOD_INIT(x)=@MARKER@x@' ../util/grub-fstest.c ../grub-core/kern/emu/hostfs.c ../grub-core/disk/host.c ../grub-core/osdep/init.c > grub_fstest.pp || (rm -f grub_fstest.pp; exit 1)
2022-07-13T08:39:10.7390670Z config.status: creating config-util.h
2022-07-13T08:39:10.7445402Z In file included from ../include/grub/osdep/hostfile_unix.h:***,
2022-07-13T08:39:10.7445785Z                  from ../include/grub/osdep/hostfile.h:6,
2022-07-13T08:39:10.7446099Z                  from ../include/grub/emu/hostfile.h:25,
2022-07-13T08:39:10.7446525Z                  from ../util/grub-fstest.c:37:
2022-07-13T08:39:10.7446914Z ./config.h:38:10: fatal error: ./config-util.h: No such file or directory
2022-07-13T08:39:10.7447259Z    38 | #include <config-util.h>
2022-07-13T08:39:10.7447522Z       |          ^~~~~~~~~~~~~~~
2022-07-13T08:39:10.7447772Z compilation terminated.

This got likely introduced when the 32-bit version of GRUB in #1819.

Reported to the mailing list, but no solution yet: https://lists.buildroot.org/pipermail/buildroot/2022-June/645339.html