chore: remove module.modulemap

[toidiu]

awslabs/aws-crt-swift#163

Description of changes:

What is module.modulemap
module.modulemap allows C code to be consumed as a clang module. Since Swift consumes s2n-tls as a clang module this file is/was necessary (this file was added by the SDK team to support Swift build). However, more recent version of Swift Packet Manager now supports auto-generating the module.modulemap so this file is not necessary.

Why remove module.modulemap
In some environments (case-insensitive file systems) we are seeing issues. Note that this is the SDK build team (same team that originally added this file) and they are asking to remove the module.modulemap since its can be auto generated from the Swift Packet Manager.

Impact
module.modulemap enables s2n-tls code to be consumes as a clang module. This therefore impacts two types of build systems: Swift and Clang.

• Swift: the impact here should be low since customers would need to be running an old version of Swift Packet Manager and typical Apple development is quite aggressive about updating development version. The risk here is non-zero but small; additionally our only known customer (SDK team) wants this change.
• Clang: a clang build system can always work around this issue by providing their own custom module.modulemap and passing custom flags to the clang compiler. The impact here is low and customers have a work around. (Note that passing custom flags to the Swift PM is not possible, hence why we needed to include module.modulemap in our repo previously.)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[lrstewart]

What effect will this have on existing Swift customers building the library? Will it break existing builds?

[dougch]

A doc issue or quick note somewhere about swift usage would be helpful.

[toidiu]

What effect will this have on existing Swift customers building the library? Will it break existing builds?

As I understand the swift build step auto-generates this file so it should not affect customers.

I have updated the description with a more detailed description of actions and summary

[toidiu]

A doc issue or quick note somewhere about swift usage would be helpful.

We dont officially support swift bindings and I am not aware of all the steps and files needed for swift bindings so I am wary of adding guidance which might be half baked.

[lrstewart]

What effect will this have on existing Swift customers building the library? Will it break existing builds?

The description was updated to answer this. This change could break customer builds, but the expected impact is still low and affected customers have workarounds.