ARM-CI: Mount Linux ARM emulator rootfs during each build

[prajwal-aithal]

• Previous PR Add CI support for Linux ARM emulator #4141 assumed that the rootfs is mounted
  throughout the lifespan of the CI machine
• Changing this to mount and unmount everytime a build is triggered

Signed-off-by: Prajwal A N an.prajwal@samsung.com

[prajwal-aithal]

@jashook @mmitche @leemgs @myungjoo

[jashook]

@dotnet-bot test ci please

[jashook]

Lgtm

[prajwal-aithal]

@jashook Does asking dotnet-bot to test CI test the manual jobs as well (Linux ARM emulator build is right now a manually triggered job)?

[prajwal-aithal]

@jashook Can we merge this to check if the ARM emulator build works correctly?

PS: The 2 CI check failures are not related to my change (they occur due to the absence of a dll file).

[mmitche]

LGTM

[prajwal-aithal]

@dotnet-bot test Linux ARM emulator build

[prajwal-aithal]

@jashook @mmitche When will the new CI script (including the changes of this PR) be in circulation within the CI system?

I tried triggering the Linux ARM emulator build on PR #5211 , but according to the logs of the build here, the contents of this PR are not yet added to the CI script.

[jashook]

It looks like it ran with the changes here: http://dotnet-ci.cloudapp.net/job/dotnet_coreclr/job/master/job/arm_cross_release_ubuntu/673/console

[jashook]

It looks like the unmount command failed so the entire build stopped and got marked as a failure? @mmitche this sound correct?

[prajwal-aithal]

@jashook @mmitche My bad. I did not think much of what happens to the whole build when a build command fails. We can fix this by changing the line dealing with mounting to
if grep -qs '/opt/linux-arm-emulator-root' /proc/mounts; then sudo umount /opt/linux-arm-emulator-root; fi ; sudo mount /opt/linux-arm-emulator/platform/rootfs-t30.ext4 /opt/linux-arm-emulator-root/

I will open a new PR to do this.

[mmitche]

If a single build step fails it will stop the rest of the build (and then execute post-build commands). So you probably want to make sure your unmount command returns 0 or tests for appropriate errors codes. Obviously if it wasn't mounted, umount would fail, but if umount fails for real reasons then we should probalby stop building