Undo workarounds added to dockerfile while updating to 7.0 SDK

[pranavkm]

As part of updating the SDK in #37192, we had to add stop-gap workarounds to eng/docker/rhel.Dockerfile and src/Installers/Rpm/Directory.Build.targets to allow the build to succeed on a CentOS 7 image. We want to eventually switch to an official image that supports building RPM packages without these hacks. This is a tracking issue to remove these workarounds.

Things to change as part of this undo:

a) Use an updated base image
b) Remove hacks to uninstall / install ruby
c) Changes made to src/Installers/Rpm/Directory.Build.targets as part of the PR

[dougbu]

@janvorli @mthalman @NikolaMilosavljevic please let us know when a working CentOS or RHEL 7 rpmpkg image is available.

[wtgodbe]

@janvorli @mthalman @NikolaMilosavljevic do we have images we can use for this?

[mthalman]

Not that I know of. The https://github.com/dotnet/dotnet-buildtools-prereqs-docker repo is a self-service repo where product teams can make PRs to define/update Dockerfiles that meet the needs of their repos. That's the process that should be followed for this.

[dougbu]

@mthalman should we update the centos-7-rpmpkg-* tag going forward or create something new (perhaps using RHEL)❔

[mthalman]

@mthalman should we update the centos-7-rpmpkg-* tag going forward or create something new (perhaps using RHEL)❔

I have no knowledge on how product teams are using the container images produced by that repo so I can't really offer any guidance here. I do know that it doesn't support building RHEL because of the licensing requirements.

[NikolaMilosavljevic]

@janvorli @mthalman @NikolaMilosavljevic do we have images we can use for this?

Can you use the same image that is used by dotnet/runtime to build RPMs today? Do you need to create a new one?

https://github.com/dotnet/runtime/blob/73665cc31f47264b70b4c9755ee2be1712b4f532/eng/pipelines/installer/jobs/base-job.yml#L29

[wtgodbe]

Let's find out: #41194

[dougbu]

We used to use another version of the same image -- mcr.microsoft.com/dotnet-buildtools/prereqs:rhel-7-rpmpkg-e1b4a89-20175311035359 and it stopped working. dotnet/runtime may use rpm directly while we use the fpm wrapper.

[NikolaMilosavljevic]

We used to use another version of the same image -- mcr.microsoft.com/dotnet-buildtools/prereqs:rhel-7-rpmpkg-e1b4a89-20175311035359 and it stopped working. dotnet/runtime may use rpm directly while we use the fpm wrapper.

Runtime build uses FPM tool, as well: https://github.com/dotnet/arcade/blob/5ef2983363df5e0d85181b2948e2a5b0c16aa41a/src/Microsoft.DotNet.Build.Tasks.Installers/build/installer.singlerid.targets#L314

[dougbu]

According to comments in #37192, our original issue w/ mcr.microsoft.com/dotnet-buildtools/prereqs:rhel-7-rpmpkg-e1b4a89-20175311035359 was related to SSL issues. @wtgodbe used the slightly older mcr.microsoft.com/dotnet-buildtools/prereqs:rhel-7-rpmpkg-c982313-20174116044113 in #41194 and instead hit a missing sudo file. Updating the prereqs image to get a CentOS 7 w/ a working fpm seems like the most straightforward way ahead.

[dougbu]

… unless of course it works to simply delete our RUN chown root:root /usr/bin/sudo && chmod 4755 /usr/bin/sudo in the Dockerfile updated in #41194 @wtgodbe