[Driver] Denote ABI type in driver invocation

[modocache]

Addresses a FIXME to specify ABI type in the driver invocation.

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See #439 for additional context.

[gribozavr]

@modocache As discussed in another PR, we'd need to change the CMake logic to put the library in a different directory. Do you have access to a Linux machine so that you can test?

[hpux735]

There are a few places to look for changes. One is cmake/modules/AddSwift:44

# Compute the library subdirectory to use for the given sdk and
# architecture, placing the result in 'result_var_name'.
function(compute_library_subdir result_var_name sdk arch)
  set("${result_var_name}" "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${arch}" PARENT_SCOPE)
endfunction()

There are quite a few places with similar references.

[hpux735]

There's another issue with ABIs that would be nice to have fixed. In the Foundation build scripts, I have to assume gnueabihf if it's an ARM, otherwise it won't build.

[gottesmm]

This sounds like something for @jrose-apple.

[modocache]

Sorry to keep this open so long. It's outdated to the point that the FIXME being addressed doesn't even exist anymore!