Add SLEEF_BUILD_SHARED_LIBS to override BUILD_SHARED_LIBS from including projects

[alexreinking]

This PR contains three contributions in corresponding commits:

1. Correct the usage of cmake_minimum_required and project to maintain compatibility with future CMake versions.
2. Add a new SLEEF_BUILD_SHARED_LIBS variable which overrides the value of BUILD_SHARED_LIBS within SLEEF's project scope when used as a submodule.
3. Remove the dummy install rules.

Parts (2-3) are meant to supersede #510.

ATTN @blapie @xuhancn

[xuhancn]

You need add Remove the dummy install rules. back, you can't pass pytorch PreCI without it. @alexreinking
Dummy install will dirty pytorch output binaries.

[alexreinking]

@xuhancn -- I don't understand your comment. This PR removes the dummy install rules. Do you mean I should revert 592edaf?

[xuhancn]

@xuhancn -- I don't understand your comment. This PR removes the dummy install rules. Do you mean I should revert 592edaf?

Install dummy will always install sleef binaries into torch/dummy directory. It will dirty pytorch output directory, and hit PreCI checkout rules.

I double checked it, your current code seems right. I will vaildate your PR later, and let you known the status. @alexreinking

[alexreinking]

I double checked it, your current code seems right. I will vaildate your PR later, and let you known the status.

Sounds good! Let me know how it goes.

[xuhancn]

@alexreinking your PR can pass pytorch Windows build.
Test in pytorch's PR: pytorch/pytorch#122053

[alexreinking]

@xuhancn - Great! Thank you for testing.

Hopefully @blapie can review soon, but only during normal working hours of course 🙂

[xuhancn]

@alexreinking your PR can pass pytorch PreCI also.

[blapie]

Thanks, really happy with this solution. Just left 1 nitty comment.

[blapie]

Brilliant, thanks! It sounds like we set ourselves for some troubles by not keeping cmake tidy.
To our defence the project has been hibernating for over 3 years, but we should probably have started with that.

Just left 1 nitty comment, otherwise happy to merge.

[xuhancn]

Brilliant, thanks! It sounds like we set ourselves for some troubles by not keeping cmake tidy. To our defence the project has been hibernating for over 3 years, but we should probably have started with that.

Just left 1 nitty comment, otherwise happy to merge.

Please merge it ASAP. Thanks.

[blapie]

@xuhancn - It's in!
@alexreinking - Thanks that was super helpful!

[alexreinking]

@blapie - you're welcome! I'm always happy to help open source projects with their build systems 🙂

[xuhancn]

@xuhancn - It's in! @alexreinking - Thanks that was super helpful!

Cool, I will update pytorch to latest sleef master.

[yuyichao]

It seems that this have disabled the generation of libsleef.so and libsleefquad.so symlinks making it harder to find/link to the library. Is this intentional?

[alexreinking]

It seems that this have disabled the generation of libsleef.so and libsleefquad.so symlinks making it harder to find/link to the library. Is this intentional?

It was not intentional. The removal of the dummy targets was done in #510. I shouldn't have assumed this change was thoroughly tested before cherry picking it blindly.

Thank you for your follow up PR fixing it properly for CMake 3.18.