Avoid compiling setup executable when cross-compiling

[sergv]

It seems currently cabal cannot know whether it cross-compiles or not, i.e. you can pass --with-ghc, --with-gcc, --with-ld etc flags pointing to cross-compiler and other tools but there's no way to tell cabal to not try building setup executable with these tools.

When build-type of a package is Simple the cabal can avoid creating setup executable and is able to cross-compile a package. But when build-type is Custom, or when, for some other reason which I haven't figured out, cabal decides to build setup executable it uses cross-compiler and executable generally cannot be runned on the platform you're compiling. And so the cross-compilation process fails even when it could be successfully finished by using /usr/bin/runghc Setup.hs (presuming that runghc is the native interpreter for the platform you`re building on).

Given the need to support Custom build types I'd like to suggest to add an option to cabal to compile Setup.hs files with user-supplied ghc or to run them with user-supplied runghc rather than compiling them with compiler from --with-ghc.

Or maybe I missed something obvious and someone can point it out.

[23Skidoo]

Yes, Cabal should be made aware of the distinction between host and build.

[cetu86]

How would you implement that? Using an additional switch like --with-build-ghc?

[23Skidoo]

Yes, something like configure --build-hc.

[rwbarton]

Isn't this the same as #1493?

[23Skidoo]

Closing in favour of #1493.