https://bugs.gentoo.org/968162

--- a/tools/defcheck.py
+++ b/tools/defcheck.py
@@ -31,7 +31,7 @@
 
 import os, sys, subprocess
 
-from os import path
+from os import getenv, path
 
 def_files = (
    "libgimpbase/gimpbase.def",
@@ -55,7 +55,7 @@
       sys.exit (-1)
 
 libextension   = ".so"
-command        = "nm --defined-only --extern-only "
+command        = getenv("NM", default="nm") + " --defined-only --extern-only "
 platform_linux = True
 
 if sys.platform in ['win32', 'cygwin']: