odd meson failure: Unknown variable "exe_name"

[Peter Maydell]

On my x86-64 Linux box, one of my local build trees turned out not
to work:

$ rm -rf build/x86 && mkdir build/x86 && (cd build/x86 &&
'../../configure'
'--target-list=arm-softmmu,aarch64-softmmu,arm-linux-user,aarch64-linux-user'
'--enable-debug' '--cc=ccache gcc' '--audio-drv-list=pa'
'--with-pkgversion=pm215' '--enable-trace-backends=log,dtrace'
'--enable-docs')

fails with
[...]
Program keycodemapdb/tools/keymap-gen found: YES
Program scripts/decodetree.py found: YES
Program ../scripts/modules/module_block.py found: YES
Program nm found: YES
Program scripts/undefsym.sh found: YES
Program scripts/feature_to_c.sh found: YES

../../meson.build:1030:14: ERROR: Unknown variable "exe_name".

A full log can be found at
/home/petmay01/linaro/qemu-from-laptop/qemu/build/x86/meson-logs/meson-log.txt

ERROR: meson setup failed


This is the same box that's worked fine for merge testing, so
presumably something about the particular set of configure
options is tripping it up.

thanks
-- PMM