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 26 seconds (queued for 8 seconds)
latest
Status Name Job ID Coverage
  Lint
passed shellcheck #40180

00:00:25

passed shfmt #40181

00:00:10

 
  Build
passed build:secure #40182
secure vm

00:03:44

 
  Test
passed test-basic-qemu #40184
fast-single-thread

00:03:08

passed test-cloudimg-qemu #40185
fast-single-thread

00:04:15

passed test-vagrant-boxes-format #40183

00:00:31