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 8 minutes and 22 seconds (queued for 6 seconds)
latest
Status Name Job ID Coverage
  Lint
passed shellcheck #37881

00:00:22

passed shfmt #37882

00:00:18

 
  Build
passed build:secure #37883
secure vm

00:03:39

 
  Test
passed test-basic-qemu #37885
fast-single-thread

00:03:09

passed test-cloudimg-qemu #37886
fast-single-thread

00:04:20

passed test-vagrant-boxes-format #37884

00:00:30