Add --enable-library-bytecode option for building bytecode libraries

[mpickering]

The new Cabal and cabal-install option tells GHC to build a bytecode library.

• When GHC is invoked, bytecode objects are also produced.
• A bytecode library is created during linking.
• The bytecode library is installed when the package is installed.
• The bytecode-library-dirs field can be populated to instruct GHC where to find the bytecode library for a package. (This can be useful if the bytecode libraries are distributed separately from the other libraries).

The bytecode object files are produced alongside an existing build way. They are prioritised in this order (-dyn-too, -dynamic, -static).

Bytecode libraries can't be produced standalone at the moment. You have to produce them alongside an existing build way. This is due to limitations in GHC.

At the moment, there is not support implemented for creating profiled bytecode libraries.

Implements haskell/cabal-proposals#2

Fixes #11188

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[geekosaur]

just a reminder: stub here

[geekosaur]

I notice that no test actually exercises the new cabal file entries as yet (which I presume exist in addition to the options, since the cabal file rev was bumped to 3.17).

[mpickering]

I notice that no test actually exercises the new cabal file entries as yet (which I presume exist in addition to the options, since the cabal file rev was bumped to 3.17).

Do you mean the project file? You're right I didn't add any tests for that, I can add some.

[mpickering]

I have fixed the #TODO which @geekosaur pointed out and added some more tests now (testing cabal.project files and trying to only build the bytecode way).