Consolidate Android cross-build setup for mono and coreclr

[am11]

The cross-build in :/eng/ requires user to pass -cross argument to :/build.sh and set ROOTFS_DIR environment variable.

During the native build, it relies on setup done by the scripts under :/eng/common/cross. We have multiple examples in our platform matrix ({os}-{arch}) which make use of this infrastructure.

Android, however, is at the odds. For coreclr, it uses setup from :/eng/common/cross/build-android-rootfs.sh and :/eng/common/cross/toolchain.cmake, but for mono it uses a different setup. The impact is that:

The cross-build in :/eng/ requires user to pass -cross argument to :/build.sh and set ROOTFS_DIR environment variable.

does not hold for "Android on mono", due to which it requires us to add a few exceptions in the build infra and need us to remember about this exceptional case. Another down side is that the coreclr Android setup gets stale every now and then because no CI leg is exercising it.

I am opening this issue to discuss what can be done to consolidate Android build on mono and coreclr without losing any flexibility and still adapt to -cross / CrossBuild infrastructure.

[am11]

cc @akoeplinger, @fanyang-mono , @ViktorHofer, @janvorli

[fanyang-mono]

Thanks for opening this issue. More discussions could be found from this PR #55641

[ghost]

Tagging subscribers to this area: @dotnet/runtime-infrastructure
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Issue Details

---

The cross-build in :/eng/ requires user to pass -cross argument to :/build.sh and set ROOTFS_DIR environment variable.

During the native build, it relies on setup done by the scripts under :/eng/common/cross. We have multiple examples in our platform matrix ({os}-{arch}) which make use this infrastructure.

Android, however, is at the odds. For coreclr, it uses setup from :/eng/common/cross/build-android-rootfs.sh and :/eng/common/cross/toolchain.cmake, but for mono it uses a different setup. The impact is that:

The cross-build in :/eng/ requires user to pass -cross and ROOTFS_DIR to ./build.sh.

does not hold for "Android on mono", due to which it requires us to add a few exceptions in the build infra and need us to remember about this exceptional case. Another down side is that the coreclr Android setup gets stale every now and then because no CI leg is exercising it.

I am opening this issue to discuss what can be done to consolidate Android build on mono and coreclr without losing any flexibility and still adapting the -cross / CrossBuild infrastructure.

Author:	am11
Assignees:	-
Labels:	area-Infrastructure
Milestone:	-

[ghost]

Tagging subscribers to 'arch-android': @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

Issue Details

---

The cross-build in :/eng/ requires user to pass -cross argument to :/build.sh and set ROOTFS_DIR environment variable.

During the native build, it relies on setup done by the scripts under :/eng/common/cross. We have multiple examples in our platform matrix ({os}-{arch}) which make use this infrastructure.

Android, however, is at the odds. For coreclr, it uses setup from :/eng/common/cross/build-android-rootfs.sh and :/eng/common/cross/toolchain.cmake, but for mono it uses a different setup. The impact is that:

The cross-build in :/eng/ requires user to pass -cross and ROOTFS_DIR to ./build.sh.

does not hold for "Android on mono", due to which it requires us to add a few exceptions in the build infra and need us to remember about this exceptional case. Another down side is that the coreclr Android setup gets stale every now and then because no CI leg is exercising it.

I am opening this issue to discuss what can be done to consolidate Android build on mono and coreclr without losing any flexibility and still adapting the -cross / CrossBuild infrastructure.

Author:	am11
Assignees:	-
Labels:	area-Infrastructure, os-android
Milestone:	-