nix's libs live in $out/lib now, not $out/nix/lib

Dependencies

• [2] FJILMA6G configure: Preserve the user's $CPPFLAGS and $LDFLAGS.
• [3] 2KJFOYGS hydra: Actually check for Nix in `configure'.
• [*] FV2M6MOT hydra: use autoconf/-make

Change contents

• replacement in configure.ac at line 66
  [2.40]→[2.40:74](∅→∅)
  − LDFLAGS="$LDFLAGS -L$nix/lib/nix"
  [2.40]

  [3.113]
  + LDFLAGS="$LDFLAGS -L$nix/lib"