gr: Use Ninja, fix version generation.

[Biswa96]

Manually generate version number otherwise CMake fails for not being git repository.

[Biswa96]

1. Use Ninja for faster build.
2. Create version.txt using pkgver variable. Otherwise, CMake shows this warning and pkgconfig files have zero version number.

CMake Warning at cmake/GetVersionFromGit.cmake:29 (message):
    Could not read version from git or version.txt
Call Stack (most recent call first):
    CMakeLists.txt:5 (get_version_from_git)

3. Also remove the -Werror which shows warnings like these:

cc1plus.exe: warning: '-Werror=' argument '-Werror=implicit' is not valid for C++

/cc @kojix2 @kou Any opinions?

[kojix2]

@Biswa96
Awesome.
I can do simple things like updating the version number or updating the sha 256, but honestly, I don't know much about difficult things. I think @kou will take a look. It's good that the time required to build is reduced.
Thanks anyway!

[kou]

+1

[kou]

Could you report this to upstream?
https://github.com/sciapp/gr/issues

[FlorianRhiem]

The compiler flag support detection should be fixed now, so that CMakeLists.txt won't assume that all GCC and Clang versions support this flag.

[kojix2]

Biswa96 has the right to report.
However, I think Biswa96 is just volunteering to help us this time, so I don't want to bother him.
I've posted a link to an existing issue on sciapp/gr.
But you can still report it as a new issue.

[Biswa96]

@lazka ready to merge.