rust/chg/build.rs

simplemerge: make merge_lines() a free function

IMO, the rendering of a conflict as text with merge markers should be
separate from the code for resolving conflicts. The latter is what
`Merge3Text` is mostly about already.

Differential Revision: https://phab.mercurial-scm.org/D11974

fn main() {
    cc::Build::new()
        .warnings(true)
        .file("src/sendfds.c")
        .file("src/sighandlers.c")
        .compile("procutil");
}