Fix $BUILD_VERSION not being passed to build-inside-vm.sh

Fixes: 3bda5b26 ("Use new experimental VM runners[1] for building")
6 jobs for master in 7 minutes and 52 seconds (queued for 8 seconds)
latest
Status Name Job ID Coverage
  Lint
passed shellcheck #37642

00:00:13

passed shfmt #37643

00:00:09

 
  Build
passed build:secure #37644
secure vm

00:03:27

 
  Test
passed test-basic-qemu #37646
fast-single-thread

00:03:32

passed test-cloudimg-qemu #37647
fast-single-thread

00:04:08

passed test-vagrant-boxes-format #37645

00:00:35