Support OpenBSD's tar where possible, require GNU tar for xz support (#2283)

[Blaisorblade]

This PR improves the support for OpenBSD's tar as discussed in #2283. For .tar.xz archives that are unsupported there, it will error out and require installing gtar. For other archives it will specify z and j options (on all platforms), hence supporting OpenBSD tar directly (and I assume staying compatible with other ones).

The first commit is already tested by @bonds on OpenBSD, I tested both on OS X, and checked manpages for GNU tar and FreeBSD tar, so this should work there too.

Relevant UNIX man pages:
OpenBSD tar
FreeBSD tar.

[bonds]

I tested the '-j' option on OpenBSD and it worked:

Before (using Version 1.1.2 x86_64 hpack-0.14.0):

~/s/winot (scott|✚3) ❯❯❯ stack setup                Mon Aug  8 11:10:17 PDT 2016
Preparing to install GHC to an isolated location.
This will not interfere with any system-level installation.
Already downloaded.                
Running /bin/tar xf /home/scott/.stack/programs/x86_64-openbsd/ghc-7.8.3.tar.bz2 in directory /tmp/stack-setup16733/ exited with ExitFailure 1


tar: input compressed with bzip2; use the -j option to decompress it

Unpacking GHC into /tmp/stack-setup16733/ ...⏎

After (using 0ae5411):

~/s/winot (scott|✚3) ❯❯❯ /home/scott/src/stack/.stack-work/install/x86_64-openbsd/lts-6.0/7.10.3/bin/stack setup
Preparing to install GHC to an isolated location.
This will not interfere with any system-level installation.
Already downloaded.                
Did not find executable at specified path: /tmp/stack-setup24687/ghc-7.8.3/configure
Configuring GHC ...⏎

Not sure about the error about not being able to find the executable...I was able to cd into the tmp directory and see all the files in there, so that appears to be a separate issue.

[Blaisorblade]

Not sure about the error about not being able to find the executable...I was able to cd into the tmp directory and see all the files in there, so that appears to be a separate issue.

I looked at the tarball from https://openbsd.dead-parrot.de/distfiles/ghc-7.8.3.20150623-amd64-unknown-openbsd.tar.bz2; I guess the directory is named /tmp/stack-setup24687/ghc-7.8.3.20150623/ rather than /tmp/stack-setup24687/ghc-7.8.3/? That explains the immediate failure; given #416 I'm sure there are bigger problems anyway. EDIT: I opened commercialhaskell/stackage-content#20 to drop it.

Looking at #416, you should be able to do a stack setup 7.10.3 --reinstall to test the 7.10.3 bindist (also .bz2). You should then be able to remove it (EDIT: if you want) with (careful!) rm -rf ~/.stack/programs/x86_64-osx/ghc-7.10.3* (please double-check). (EDIT2: #416 (comment) reports some small problems with that bindist, so beware).

[bonds]

LGTM:

~ ❯❯❯ stack setup 7.10.3 --reinstall                Mon Aug  8 14:29:12 PDT 2016
Preparing to install GHC to an isolated location.
This will not interfere with any system-level installation.
Already downloaded.                 
Running /bin/tar xf /home/scott/.stack/programs/x86_64-openbsd/ghc-7.10.3.tar.bz2 in directory /tmp/stack-setup16994/ exited with ExitFailure 1


tar: input compressed with bzip2; use the -j option to decompress it

Unpacking GHC into /tmp/stack-setup16994/ ...⏎                                  
~ ❯❯❯ /home/scott/src/stack/.stack-work/install/x86_64-openbsd/lts-6.0/7.10.3/bin/stack setup 7.10.3 --reinstall
Run from outside a project, using implicit global project config
Using resolver: lts-6.9 from implicit global project's config file: /home/scott/.stack/global-project/stack.yaml
Populated index cache.    
Preparing to install GHC to an isolated location.
This will not interfere with any system-level installation.
Already downloaded.                 
Installed GHC.                              
stack will use a sandboxed GHC it installed
For more information on paths, see 'stack path' and 'stack exec env'
To use this GHC and packages outside of a project, consider using:
stack ghc, stack ghci, stack runghc, or stack exec
~ ❯❯❯                                               Mon Aug  8 14:31:56 PDT 2016