kernel/common builds hang when trying to boot via EFI

[nathanchance]

[   11.368919] Run /init as init process
[   11.501012] mkdir (955) used greatest stack depth: 12928 bytes left
Starting syslogd: OK
Starting klogd: OK
Initializing random number generator... [   11.931583] random: dd: uninitialized urandom read (512 bytes read)
done.
Starting network: [   12.220954] wait_iface (981) used greatest stack depth: 12656 bytes left
[   12.332104] ip (982) used greatest stack depth: 12320 bytes left
OK
Linux version 4.19.67-g281eb60c2 (driver@clangbuiltlinux) (clang version 9.0.0-svn366197-1~exp1+0~20190716095603.167~1.gbp7d3830 (trunk)) #1 SMP PREEMPT Thu Jan 1 00:00:00 UTC 1970
Linux version 4.19.67-g281eb60c2 (driver@clangbuiltlinux) (clang version 9.0.0-svn366197-1~exp1+0~20190716095603.167~1.gbp7d3830 (trunk)) #1 SMP PREEMPT Thu Jan 1 00:00:00 UTC 1970
Stopping network: OK
Saving random seed... [   12.969817] random: dd: uninitialized urandom read (512 bytes read)
done.
Stopping klogd: OK
Stopping syslogd: OK
umount: devtmpfs busy - remounted read-only
umount: can't unmount /: Invalid argument
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system poweroff
[   15.351335] reboot: System halted
root@91bab6d8861f:/ci2# echo $?
124

Full build logs: https://travis-ci.com/nathanchance/continuous-integration/builds/123430893

This is split off from #199 based on @kees' request. This can be reproduced on #199 with the following diff:

diff --git a/driver.sh b/driver.sh
index 545af0c..79ddef1 100755
--- a/driver.sh
+++ b/driver.sh
@@ -89,7 +89,7 @@ setup_variables() {
                      -device "virtio-blk-device,drive=rootfs"
                      -append "console=ttyAMA0 earlycon root=/dev/vda" )
       aavmf=/usr/share/AAVMF
-      if [[ ${tree} != common && -f ${aavmf}/AAVMF_CODE.fd && -f ${aavmf}/AAVMF_VARS.fd ]]; then
+      if [[ -f ${aavmf}/AAVMF_CODE.fd && -f ${aavmf}/AAVMF_VARS.fd ]]; then
         cp ${aavmf}/AAVMF_VARS.fd images/arm64
         qemu_cmdline+=( -drive "if=pflash,format=raw,readonly,file=${aavmf}/AAVMF_CODE.fd"
                         -drive "if=pflash,format=raw,file=images/arm64/AAVMF_VARS.fd" )
@@ -155,7 +155,7 @@ setup_variables() {
                          -append "console=ttyS0 root=/dev/vda" ) ;;
       esac
       ovmf=/usr/share/OVMF
-      if [[ ${tree} != common && -f ${ovmf}/OVMF_CODE.fd && -f ${ovmf}/OVMF_VARS.fd ]]; then
+      if [[ -f ${ovmf}/OVMF_CODE.fd && -f ${ovmf}/OVMF_VARS.fd ]]; then
         cp ${ovmf}/OVMF_VARS.fd images/x86_64
         qemu_cmdline+=( -drive "if=pflash,format=raw,readonly,file=${ovmf}/OVMF_CODE.fd"
                         -drive "if=pflash,format=raw,file=images/x86_64/OVMF_VARS.fd" )

[nickdesaulniers]

cc @Ajs1984 , is this something of interest?