To ensure libiconv can be found by Guix, we need to link the library.

--- a/setup.py
+++ b/setup.py
@@ -81,8 +81,7 @@ else:
     libraries.extend(["m", "z"])
     _platform = sys.platform
     # Mac: iconv needs to be linked statically
-    if _platform.lower().startswith("darwin"):
-        libraries.append("iconv")
+    libraries.append("iconv")
 
 # Extensions
 sources.sort()