pc-bios: ensure keymaps dependencies set vnc tests

pc-bios: ensure keymaps dependencies set vnc tests

I was seeing failures on vnc-display-test on FreeBSD:

  make vm-build-freebsd V=1 TARGET_LIST=aarch64-softmmu BUILD_TARGET=check-qtest QEMU_LOCAL=1 DEBUG=1

Leads to:

  qemu-system-aarch64: -vnc none: could not read keymap file: 'en-us'
  Broken pipe
  ../src/tests/qtest/libqtest.c:196: kill_qemu() tried to terminate QEMU process but encountered exit status 1 (expected 0)

which was as far as I could tell because we don't populate the
$BLD/pc-bios/keymaps (although scripts/symlink-install-tree.py
attempts to symlink qemu-bundle/usr/local/share/qemu/keymaps/ to that
dir).

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250108121054.1126164-31-alex.bennee@linaro.org>