[WIP] fix windows CI

[erip]

Per actions/runner-images/issues/2667

There is certainly a more elegant way to do this, but environment variables in GitHub Actions are weird.

[kpu]

Thanks for looking at this! Now Windows CI can't find boost:

CMake Error at C:/Program Files/CMake/share/cmake-3.22/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find Boost (missing: Boost_INCLUDE_DIR program_options system
  thread unit_test_framework) (Required is at least version "1.41.0")
Call Stack (most recent call first):
  C:/Program Files/CMake/share/cmake-3.22/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  C:/Program Files/CMake/share/cmake-3.22/Modules/FindBoost.cmake:2375 (find_package_handle_standard_args)
  CMakeLists.txt:85 (find_package)

(The Ubuntu failure was just package management being annoying, I'll fix that.)

[erip]

Hmm, this is the same error as on master. I'll need to dig a bit more to understand this. I may be passing the wrong boost root.

Edit, yes, it seems like the x86_64 bit is required... cf marian's CI script. That is probably a good reference to make this PR less fragile.

[erip]

Fixing the path is a good start, but it seems like the linker is failing to load optimized.lib on Windows. I'm not sure what this is -- some intermediate build artifact in release mode? Some poking around suggests this can happen when a list isn't expanded appropriately in cmake (say, by strifigying lists) which can break the search path. However, removing quotes here breaks everything in all platforms 🙀

Locally on my Mac:

CMake Error at util/CMakeLists.txt:38 (add_library):
  Target "kenlm_util" links to target
  "$<BUILD_INTERFACE:Boost::program_options" but the target was not found.
  Perhaps a find_package() call is missing for an IMPORTED target, or an
  ALIAS target is missing?


CMake Error at util/CMakeLists.txt:38 (add_library):
  Target "kenlm_util" links to target "Boost::unit_test_framework>" but the
  target was not found.  Perhaps a find_package() call is missing for an
  IMPORTED target, or an ALIAS target is missing?

[kpu]

I'm not sure what's up with the mac

# We need boost
find_package(Boost 1.41.0 REQUIRED COMPONENTS
  program_options
  system
  thread
  unit_test_framework
)

Do you want me to merge this on the basis that windows at least goes further before failing?

[erip]

No, I'd like this to be merged once CI is green. I've marked it a WIP in case it wasn't obvious that this is a WIP. I'll spend more time trying to figure this out.