Provide separate functions for bin_extension and solo5_bindings_pkg

These two things are hardly related, keep them separate

lib/mirage.ml

@@ -240,7 +240,7 @@ module Project = struct
           package ~min:"6.0.0" ~max:"7.0.0" "mirage-xen" ::
           common
         | #Mirage_key.mode_solo5 as tgt ->
-          package ~min:"0.6.0" ~max:"0.7.0" ~ocamlfind:[] (fst (Mirage_configure_solo5.solo5_bindings_pkg tgt)) ::
+          package ~min:"0.6.0" ~max:"0.7.0" ~ocamlfind:[] (Mirage_configure_solo5.solo5_bindings_pkg tgt) ::
           package ~min:"0.6.1" ~max:"0.7.0" "mirage-solo5" ::
           common
 

lib/mirage_configure.ml

@@ -33,7 +33,7 @@ let opam_path ~name = Fpath.(v name + "opam")
 
 let artifact ~name = function
   | #Mirage_key.mode_solo5 | #Mirage_key.mode_xen as tgt ->
-    let ext = snd (Mirage_configure_solo5.solo5_bindings_pkg tgt) in
+    let ext = Mirage_configure_solo5.bin_extension tgt in
     let file = Fpath.v (name ^ ext) in
     file, file
   | #Mirage_key.mode_unix ->

lib/mirage_configure_solo5.ml

@@ -47,13 +47,23 @@ let generate_manifest_c () =
   Log.info (fun m -> m "executing %a" Bos.Cmd.pp cmd);
   Bos.OS.Cmd.run cmd
 
+let bin_extension = function
+  | `Virtio -> ".virtio"
+  | `Muen -> ".muen"
+  | `Hvt -> ".hvt"
+  | `Genode -> ".genode"
+  | `Spt -> ".spt"
+  | `Xen | `Qubes -> ".xen"
+  | _ ->
+    invalid_arg "extension only defined for solo5 targets"
+
 let solo5_bindings_pkg = function
-  | `Virtio -> "solo5-bindings-virtio", ".virtio"
-  | `Muen -> "solo5-bindings-muen", ".muen"
-  | `Hvt -> "solo5-bindings-hvt", ".hvt"
-  | `Genode -> "solo5-bindings-genode", ".genode"
-  | `Spt -> "solo5-bindings-spt", ".spt"
-  | `Xen | `Qubes -> "solo5-bindings-xen", ".xen"
+  | `Virtio -> "solo5-bindings-virtio"
+  | `Muen -> "solo5-bindings-muen"
+  | `Hvt -> "solo5-bindings-hvt"
+  | `Genode -> "solo5-bindings-genode"
+  | `Spt -> "solo5-bindings-spt"
+  | `Xen | `Qubes -> "solo5-bindings-xen"
   | _ ->
     invalid_arg "solo5 bindings package only defined for solo5 targets"
 
@@ -66,7 +76,7 @@ let solo5_platform_pkg = function
 let cflags pkg = pkg_config pkg ["--cflags"]
 
 let compile_manifest target =
-  let bindings, _post = solo5_bindings_pkg target in
+  let bindings = solo5_bindings_pkg target in
   let c = "_build/manifest.c" in
   let obj = "_build/manifest.o" in
   cflags bindings >>= fun cflags ->

lib/mirage_configure_solo5.mli

@@ -3,7 +3,9 @@ open Rresult
 val solo5_manifest_path : Fpath.t
 val clean_manifest : unit -> (unit, [> R.msg ]) result
 
-val solo5_bindings_pkg : [> Mirage_key.mode_solo5 | Mirage_key.mode_xen ] -> string * string
+val bin_extension : [> Mirage_key.mode_solo5 | Mirage_key.mode_xen ] -> string
+
+val solo5_bindings_pkg : [> Mirage_key.mode_solo5 | Mirage_key.mode_xen ] -> string
 val solo5_platform_pkg : [> Mirage_key.mode_solo5 | Mirage_key.mode_xen ] -> string
 
 val generate_manifest_json : bool -> unit -> (unit, [> R.msg ]) result

lib/mirage_impl_ip.ml

@@ -38,7 +38,7 @@ let right_tcpip_library ?ocamlfind ~sublibs pkg =
   Key.match_ Key.(value target) @@ function
   | #Mirage_key.mode_unix ->
     [ package ~min ~max ?ocamlfind ~sublibs:("unix"::sublibs) pkg ]
-  | _ ->
+  | #Mirage_key.mode_xen | #Mirage_key.mode_solo5 ->
     [ package ~min ~max ?ocamlfind ~sublibs pkg ]
 
 let ipv4_keyed_conf ~ip ?gateway () = impl @@ object

lib/mirage_link.ml

@@ -34,14 +34,15 @@ let link info name target _target_debug =
     Bos.OS.Cmd.run link >>= fun () ->
     Ok name
   | #Mirage_key.mode_solo5 | #Mirage_key.mode_xen ->
-    let bindings, post = Mirage_configure_solo5.solo5_bindings_pkg target in
+    let bindings = Mirage_configure_solo5.solo5_bindings_pkg target in
     let platform = Mirage_configure_solo5.solo5_platform_pkg target in
     extra_c_artifacts "freestanding" libs >>= fun c_artifacts ->
     static_libs platform
     >>= fun static_libs ->
     ldflags bindings >>= fun ldflags ->
     ldpostflags bindings >>= fun ldpostflags ->
-    let out = name ^ post in
+    let extension = Mirage_configure_solo5.bin_extension target in
+    let out = name ^ extension in
     let ld = find_ld bindings in
     let linker =
       Bos.Cmd.(v ld %% of_list ldflags % "_build/main.native.o" %