Support to build driver and nupkgs for armel (debian.8-armel and tizen.4.0.0-armel)

[jyoungyun]

Debian for armel

Use armel instead of arm-softfp for rootfs

• Replace arm-softfp with armel in cross/build-rootfs.sh
• Rename directory cross/arm-softfp to cross/armel
• Add toolchain.cmake file for armel
• Use stable debian jessie
• Use lldb-3.5-dev because other versions are not supported by jessie/armel repostiory

Support armel build for debian.8-armel

• Add armel architecture for building drivers in src/corehost/build.sh
• Generate debian.8-armel nupkgs and tarball

Finally I got a dotnet-debian.8-armel.1.2.0-beta-001271-00.tar.gz file by using fallback source for CoreCLR, CoreFX debian.8-armel nupkgs which have not yet been added to NuGet server.

Test command:

./build.sh --skiptests --env-vars DISABLE_CROSSGEN=1,TARGETPLATFORM=armel,TARGETRID=debian.8-armel,CROSS=1,ROOTFS_DIR=/home/jyoung/git/dotnet/rootfs/armel

Tarball:
dotnet-debian.8-armel.1.2.0-beta-001271-00.tar.gz

Tizen

Add Tizen rootfs for armel

• Most of this commit is copied from CoreCLR.

Support to create nupkgs and tarball for tizen.4.0.0-armel

• Generate tizen.4.0.0-armel nupkgs and tarball

Test command:

./build.sh -c Release --skiptests --env-vars DISABLE_CROSSGEN=1,TARGETPLATFORM=armel,TARGETRID=tizen.4.0.0-armel,CROSS=1,ROOTFS_DIR=/home/jyoung/git/dotnet/rootfs/armel-tizen

Tarball:
dotnet-tizen.4.0.0-armel.1.2.0-beta-001273-00.tar.gz

Related issue: #725 , dotnet/coreclr#8827, dotnet/corefx#14792

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[jyoungyun]

/cc @gkhanna79 @hqueue @hseok-oh
I tested the result tarball in debian.8-armel docker image and it worked well.

root@3f699365020b:/dotnet/shared/Microsoft.NETCore.App/1.2.0-beta-001271-00# ./dotnet hello.exe 
Hello World

root@3f699365020b:/dotnet/shared/Microsoft.NETCore.App/1.2.0-beta-001271-00# cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

[hqueue]

Glad to see that armel (softfp) works :)

[gkhanna79]

@ramarag @schellap PTAL as well.

[gkhanna79]

CC @janvorli

[janvorli]

@mikem8361 Do you happen to remember why we have required to use lldb-3.6 as the minimum version? This makes the ARM build use lldb-3.5 and I want to make sure we are not missing something.

[mikem8361]

I think some SOS commands 3.6 worked better 3.5 at the time and what is installed on the build machines. We really should be building against 3.8 or even 3.9, but just haven’t got the CI lab to upgrade yet.

[jyoungyun]

@ramarag @schellap @gkhanna79 Is there anything to do more? :)

[jyoungyun]

@gkhanna79 Could you share me why this patch does not merge? If there is something more important than this or if there is an issue that merges this, I hope it will be shared with us.

[hqueue]

@gkhanna79 Since there is no enough debian 8.0 infra for test yet, tizen is our main development target platform for armel right now. As you may already know, ARM32 CI for CoreClr is also using Tizen rootfs for compiling CoreClr and running tests in tizen environment.
If you think there are too many ARM Linux legs and want to reduce them for armel, then I carefully suggest Tizen for armel instead of debian, since ARM CI with Tizen rootfs has been used for last year and we have much more interested in it.
BTW for arm devices such as raspberry pi series, I think most developers uses arm(hardfp) in rpi2 and rpi3 rather than armel(softfp), because default Linux distro for them are usually in arm(hardfp).

[gkhanna79]

Thanks for the explanation @hqueue. This sounds reasonable to me.

That said, we need to have two kinds of Arm32 builds - ones which are built for armel and the other for armhr (which is the Linux Arm32 official build support I am working on).