Don't check if configure indicated checks won't work. This should fix a
FTBFS on mipsel, where configure correctly detects the checks won't work,
while garbage is returned for disk space info at git-annex runtime. It also
means that, when built via cabal, disk space checks are not enabled,
unfortunatly.
Rather than running make, which runs configure, let Setup.hs just include
the configure code. The standalone configure is retained for use by the
Makefile.
This may work better with cabal-dev, since it avoids the Makefile running
ghc, and lets cabal handle all the compiler running, with whatever
flags it uses to expose dependencies.
