allow macOS linker to ignore undefined symbols

Author: malt3

Diff for: haskell/private/actions/link.bzl

@@ -141,6 +141,10 @@ def link_binary(
         args.add(paths.join(ar_bindir, "otool"), format = "-pgmotool=%s")
         args.add(paths.join(ar_bindir, "install_name_tool"), format = "-pgminstall_name_tool=%s")
 
+        # Allow the macOS linker to resolve undefined symbols
+        # by performing a dynamic lookup at runtime
+        args.add("-optl-undefined,dynamic_lookup")
+
     args.add_all(hs.toolchain.ghcopts)
     args.add_all(compiler_flags)
 
@@ -382,6 +386,10 @@ def link_library_dynamic(hs, cc, posix, dep_info, extra_srcs, object_files, my_p
         args.add(paths.join(ar_bindir, "otool"), format = "-pgmotool=%s")
         args.add(paths.join(ar_bindir, "install_name_tool"), format = "-pgminstall_name_tool=%s")
 
+        # Allow the macOS linker to resolve undefined symbols
+        # by performing a dynamic lookup at runtime
+        args.add("-optl-undefined,dynamic_lookup")
+
     args.add_all(hs.toolchain.ghcopts)
     args.add_all(compiler_flags)