mc: stop retaining configure arguments in the final binary
mc: stop retaining configure arguments in the final binary

Reduces closure size of cross-compiled binary a bit by not retaining
build-time perl and friends.

Before:

    $ nix path-info -Sh $(nix-build -A pkgsCross.ppc64.mc) | unnix
    /<<NIX>>/mc-powerpc64-unknown-linux-gnu-4.8.28   273.7M

After:

    $ nix path-info -Sh $(nix-build -A pkgsCross.ppc64.mc) | unnix
    /<<NIX>>/mc-powerpc64-unknown-linux-gnu-4.8.28   198.6M

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