Move dotslash into fbcode/scm/hg/exec and add to the release script.

Summary:
This change is to get DotSlash (https://fb.quip.com/7BbiAmxAK09T)
in the Mercurial release. It renames the build rule from `dotslash` to
`dsl` under the assumption that that determines the name of the binary
to be deployed.

Reviewed By: quark-zju

Differential Revision: D13868779

fbshipit-source-id: dd44d874a60ab85b3dcca79ba5076a6f2fa64135

setup.py

@@ -2181,6 +2181,10 @@ rustextbinaries = [
     RustBinary("indexedlog_dump", manifest="exec/utils/Cargo.toml"),
 ]
 
+if havefb:
+    rustextbinaries.append(RustBinary("dotslash", manifest="exec/fb/dotslash/Cargo.toml"))
+
+
 setup(
     name="edenscm",
     version=setupversion,