qemu test-qga failure on mergebuild after VERSION file change: dependency issues??

[Peter Maydell]

The first merge I tried to process after bumping VERSION for rc0
failed on test-qga like this:

MALLOC_PERTURB_=${MALLOC_PERTURB_:-$(( ${RANDOM:-0} % 255 + 1))}
tests/test-qga -m=quick -k --tap < /dev/null | ./scripts/tap-driv
er.pl --test-name="test-qga"
PASS 1 test-qga /qga/sync-delimited
PASS 2 test-qga /qga/sync
PASS 3 test-qga /qga/ping
**
ERROR:/home/petmay01/linaro/qemu-for-merges/tests/test-qga.c:303:test_qga_info:
assertion failed (version == QEMU_VERSION): ("5.0.9
0" == "5.0.50")
ERROR test-qga - Bail out!
ERROR:/home/petmay01/linaro/qemu-for-merges/tests/test-qga.c:303:test_qga_info:
assertion failed (versio
n == QEMU_VERSION): ("5.0.90" == "5.0.50")
Aborted (core dumped)
/home/petmay01/linaro/qemu-for-merges/tests/Makefile.include:659:
recipe for target 'check-unit' failed

Looking at timestamps on files, tests/test-qga.o never got rebuilt,
even though config-host.h has been updated (and so has the new
QEMU_VERSION). Any idea what's gone wrong here?

Also weird: this build tree has no .d files in it.

thanks
-- PMM