allow reading PKG_CONFIG_ARGN

Signed-off-by: Antonio Nuno Monteiro <[email protected]>

otherlibs/configurator/src/v1.ml

@@ -616,6 +616,7 @@ let which t prog =
 module Pkg_config = struct
   type nonrec t =
     { pkg_config : string
+    ; pkg_config_args : string list
     ; configurator : t
     }
 
@@ -625,8 +626,13 @@ module Pkg_config = struct
       | s -> s
       | exception Not_found -> "pkg-config"
     in
+    let pkg_config_args =
+      match Sys.getenv "PKG_CONFIG_ARGN" with
+      | s -> String.split ~on:' ' s
+      | exception Not_found -> []
+    in
     Option.map (which c pkg_config_exe_name) ~f:(fun pkg_config ->
-        { pkg_config; configurator = c })
+        { pkg_config; pkg_config_args; configurator = c })
 
   type package_conf =
     { libs : string list
@@ -688,7 +694,8 @@ module Pkg_config = struct
       let run what =
         match
           String.trim
-            (Process.run_capture_exn c ~dir ?env t.pkg_config [ what; package ])
+            (Process.run_capture_exn c ~dir ?env t.pkg_config
+               (t.pkg_config_args @ [ what; package ]))
         with
         | "" -> []
         | s -> String.extract_blank_separated_words s

src/dune_rules/pkg_config.ml

@@ -20,12 +20,18 @@ module Query = struct
     | Libs s -> sprintf "%s.libs" s
     | Cflags s -> sprintf "%s.cflags" s
 
-  let to_args t : _ Command.Args.t list =
+  let to_args t ~env : _ Command.Args.t list =
+    let env_args : _ Command.Args.t list =
+      match Env.get env "PKG_CONFIG_ARGN" with
+      | Some s -> [ As (String.split_on_char ~sep:' ' s) ]
+      | None -> []
+    in
     Hidden_deps Dep.(Set.singleton universe)
-    ::
-    (match t with
-    | Libs lib -> [ A "--libs"; A lib ]
-    | Cflags lib -> [ A "--cflags"; A lib ])
+    :: (env_args
+       @
+       match t with
+       | Libs lib -> [ A "--libs"; A lib ]
+       | Cflags lib -> [ A "--cflags"; A lib ])
 
   let default = function
     | Libs lib -> [ sprintf "-l%s" lib ]
@@ -60,8 +66,9 @@ let gen_rule sctx ~loc ~dir query =
   | Error _ -> Memo.return @@ Error `Not_found
   | Ok _ as bin ->
     let command =
+      let env = Super_context.context_env sctx in
       Command.run ~dir:(Path.build dir) ~stdout_to:(Query.file ~dir query) bin
-        (Query.to_args query)
+        (Query.to_args ~env query)
     in
     let+ () = Super_context.add_rule sctx ~loc ~dir command in
     Ok ()