GHC doesn't compile

[Peter Simons]

Simon Peyton-Jones writes:

 > If I had a dollar for every time something bizarre happened with
 > readline, I'd be a rich man.

The problem is the configure script. In aclocal.m4, there is
a test, which tries to determine whether ar(1) supports
"-input" or not, but the test doesn't work. It runs the
command

  /usr/bin/ar q conftest.a -input /dev/null

and expects ar to terminate with an error code if "-input"
is unsupported. Ar, however, does not return an error:

  $ /usr/bin/ar q conftest.a -input /dev/null && echo bug
  /usr/bin/ar: creating conftest.a
  /usr/bin/ar: '-input': No such file
  /usr/bin/ar: Warning: '/dev/null' is not an ordinary file
  bug

Once I manually set $(ArSupportsInput) to the empty string
in mk/config.mk, the build works fine.

Since the build system obviously works without "-input",
maybe it's a good idea to drop this test altogether?

Peter