Issue #28258: Explain the LC_ALL change in a comment

Makefile.pre.in

@@ -1623,6 +1623,10 @@ distclean: clobber
 		Modules/Setup Modules/Setup.local Modules/Setup.config \
 		Modules/ld_so_aix Modules/python.exp Misc/python.pc
 	-rm -f python*-gdb.py
+	# Issue #28258: set LC_ALL to avoid issues with Estonian locale.
+	# Expansion is performed here by shell (spawned by make) itself before
+	# arguments are passed to find. So LC_ALL=C must be set as a separate
+	# command.
 	LC_ALL=C; find $(srcdir)/[a-zA-Z]* '(' -name '*.fdc' -o -name '*~' \
 				     -o -name '[@,#]*' -o -name '*.old' \
 				     -o -name '*.orig' -o -name '*.rej' \