[lldb/testsuite] Make TestObjCIvarStripped.py working with codesigning

This test was stripping a binary generated by Makefile.rules which is
potentially codesigned. Stripping invalidates the code signature, so
we might need to re-sign after stripping.

lldb/test/API/lang/objc/objc-ivar-stripped/Makefile

@@ -3,7 +3,10 @@ LD_EXTRAS := -lobjc -framework Foundation
 
 all:        a.out.stripped
 
+include Makefile.rules
+
 a.out.stripped: a.out.dSYM
 	strip -o a.out.stripped a.out
-
-include Makefile.rules
+ifneq "$(CODESIGN)" ""
+	$(CODESIGN) -fs - a.out.stripped
+endif