fix(lake): use response files on all platforms to avoid ARG_MAX

Lake already uses response files (`@file`) on Windows to avoid
exceeding CLI length limits. This extends that behavior to macOS
and Linux, where linking Mathlib's ~15,000 object files into a
shared library exceeds macOS's ARG_MAX (262,144 bytes).

Both `clang` and `gcc` support `@file` response files on all
platforms, so this is safe to enable unconditionally.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kim-em

src/lake/Lake/Build/Actions.lean

@@ -87,21 +87,20 @@ public def compileO
   }
 
 public def mkArgs (basePath : FilePath) (args : Array String) : LogIO (Array String) := do
-  if Platform.isWindows then
-    -- Use response file to avoid potentially exceeding CLI length limits.
-    let rspFile := basePath.addExtension "rsp"
-    let h ← IO.FS.Handle.mk rspFile .write
-    args.forM fun arg =>
-      -- Escape special characters
-      let arg := arg.foldl (init := "") fun s c =>
-        if c == '\\' || c == '"' then
-          s.push '\\' |>.push c
-        else
-          s.push c
-      h.putStr s!"\"{arg}\"\n"
-    return #[s!"@{rspFile}"]
-  else
-    return args
+  -- Use response file to avoid potentially exceeding CLI length limits.
+  -- On Windows this is always needed; on macOS/Linux this is needed for large
+  -- projects like Mathlib where the number of object files exceeds ARG_MAX.
+  let rspFile := basePath.addExtension "rsp"
+  let h ← IO.FS.Handle.mk rspFile .write
+  args.forM fun arg =>
+    -- Escape special characters
+    let arg := arg.foldl (init := "") fun s c =>
+      if c == '\\' || c == '"' then
+        s.push '\\' |>.push c
+      else
+        s.push c
+    h.putStr s!"\"{arg}\"\n"
+  return #[s!"@{rspFile}"]
 
 public def compileStaticLib
   (libFile : FilePath) (oFiles : Array FilePath)