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 55 seconds (queued for 10 seconds)
latest
Status Name Job ID Coverage
  Lint
passed shellcheck #37468

00:00:13

passed shfmt #37469

00:00:10

 
  Build
passed build:secure #37470
secure vm

00:03:21

 
  Test
passed test-basic-qemu #37472
fast-single-thread

00:03:06

passed test-cloudimg-qemu #37473
fast-single-thread

00:04:19

passed test-vagrant-boxes-format #37471

00:00:28