Fix CMake build on Linux

[gmittert]

• TestHelpers has a implicit dependency on Foundation through
  ArgumentParser, so it needs to link against Foundation
• The find package calls should be REQUIRED and CONFIG so they can take
  advantage of CMake configs

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

[gmittert]

@swift-ci please test platform

[gmittert]

ping @natecook1000

[natecook1000]

@swift-ci Please test

[natecook1000]

@gmittert Thanks for the contribution! I don't think our CI testing exercises the CMake build path yet — can you tell me the configuration where you're seeing this go wrong, so that I can verify locally?

[natecook1000]

@compnerd Would you mind giving this a review?

[compnerd]

Nit: would be nice to do one entry per line

[compnerd]

I'm worried about this part of the change. With this it is impossible to actually build with a prebuilt toolchain image. The CONFIG is fine, the REQUIRED is the piece that worries me.

[gmittert]

I'll remove both the QUIET and the REQUIRED then. My main concern was that it was silently failing and was a pain to debug why.

[compnerd]

The thing is that it isn't an absolutely required thing - so the non QUIET form could be confusing too. But I would be fine with it being non-quiet as long as it is not required.

[gmittert]

@natecook1000 The precise invocation I use is a little complex since we have a lot of infrastructure to support cross compiling so I'm unfortunately not able to give you a command to run, but it's something like:

cmake -G Ninja
-DCMAKE_MAKE_PROGRAM="/usr/bin/ninja"
-DCMAKE_BUILD_TYPE="Release"
-DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_INSTALL_PREFIX=
-DTOOLCHAIN_SOURCE_DIR=/data/users/gwenm/toolchain
-DTOOLCHAIN_BUILD_DIR=/data/users/gwenm/toolchain/build/Release
-DCMAKE_TRY_COMPILE_PLATFORM_VARIABLES=TOOLCHAIN_SOURCE_DIR
-DCMAKE_TOOLCHAIN_FILE="/path/to/platform/specific/toolchain/file"
-DUSE_CMAKE_INSTALL=YES
-Ddispatch_DIR=/path/to/swift-corelibs-libdispatch/cmake/modules
-DFoundation_DIR=/path/to/swift-corelibs-foundation/cmake/modules
-DXCTest_DIR=/path/to/swift-corelibs-xctest/cmake/modules
-C "/path/to/platform/specific/cache/vars/linux-x86_64.cmake"
/data/users/gwenm/toolchain_dev/external/swift-argument-parser

But really the important part is configuring via setting Xyz_DIR to locally build projects instead of building against a prebuilt toolchain.

[compnerd]

@gmittert - most of that is specific to the setup that you are building in. (e.g. the caches). I think that it is probably easier to explain with the CI I have setup on Azure (https://github.com/compnerd/swift-build/blob/master/swift-argument-parser.yml)

cmake ^
      -B $(Build.BinariesDirectory)/swift-argument-parser ^
      -D BUILD_SHARED_LIBS=YES ^
      -D BUILD_TESTING=NO ^
      -D CMAKE_BUILD_TYPE=Release ^
      -D CMAKE_Swift_COMPILER=S:\b\1\bin\swiftc.exe ^
      -G Ninja ^
      -S $(Build.SourcesDirectory)/swift-argument-parser

This is Windows specific, but very easy to generalize to other platforms. The important thing is to use a swift compiler from a swift build tree rather than than from an installed image.

[gmittert]

Alright, updated the line spacing and removed REQUIRED. @compnerd exactly, my particular set up isn't particularly optimized for external reproducibility, but the important part is building against locally built dependencies a la the Windows build.

[gmittert]

@swift-ci please test platform

[compnerd]

LGTM

[natecook1000]

Thanks to you both!

@swift-ci Please test