[alembic] linux fixes

[fabiencastan]

Describe the pull request

• What does your PR fix? Fixes issue #

Fix the portfile to avoid windows-specific commands.
Fix a linux build error due to -Werror in the library in debug mode. The build issue has been also reported to the main repository alembic/alembic#263.

• Which triplets are supported/not supported? Have you updated the CI baseline?

The alembic port file was valid only for windows. This PR adds the support for linux.
Tested on windows-10 and ubuntu-18.04.

• Does your PR follow the maintainer guide?

Yes

[msftclas]

All CLA requirements met.

[LilyWangL]

Thanks for your PR! Can you please correct the Version field in the CONTROL file? You can get more information from maintainer-guide.md.

[fabiencastan]

I'm not sure if I should update the version number, as it doesn't change anything on windows. And on linux it has never been possible to build before, so there is no need for invalidation either.

[LilyWangL]

I'm not sure if I should update the version number, as it doesn't change anything on windows. And on linux it has never been possible to build before, so there is no need for invalidation either.

You need update the version in CONTROL.

[fabiencastan]

Ok, updated.

[LilyWangL]

Could you please remove alembic:x64-linux=fail in scripts/ci.baseline.txt, it makes Linux build failed.

[fabiencastan]

Changed. I was not aware of this mechanism.
Thanks.

[ras0219-msft]

Thanks for the PR @fabiencastan!

Could you please revert the line ending change from LF to CRLF in ports/alembic/portfile.cmake? I tried pushing the change to your branch, however you did not select the "accept changes from maintainers" box.

[fabiencastan]

Hi @ras0219-msft,
I updated the history to fix the mistake on the line ending.
(I do not find the option to allow the editing of the PR, maybe because it's a fork from an organization and not from my personal account)
Best,

[strega-nil]

LGTM! Thanks @fabiencastan