enable building mueval as a dynamic executable

[int-e]

Can we either remove the hard-coded -static from mueval's cabal file, or add a flag for switching that off? The main benefit of using a dynamically built mueval is that loading packages becomes much faster (at least under GNU/Linux), because ordinary shared libraries are used instead of the built-in linker.

Background: The hard-coded -static used to be necessary for mueval to work. However, starting with the latest release (version 0.7), hint detects a dynamic RTS and switches to the dynamic way for loading packages [1]. This means that it is no longer necessary to build mueval as a static executable.

[1] hint patch: https://github.com/mvdan/hint/commit/1179e4e14963b3aba9a0858edcf6a18cfd72070e