gdb/python: fix gdb.Objfile.__repr__ () for dynamically compiled code

While experimenting with JIT reader API I realized that calling repr ()
on objfile created by JIT reader crashes GDB.

The problem was that objfpy_repr () called objfile_filename () which
returned NULL, causing PyString_FromFormat () to crash.

This commit fixes this problem by using objfile_name () instead of
objfile_filename (). This also makes consistent with the value of gdb.Objfile.filename variable.

gdb/python/py-objfile.c

@@ -513,7 +513,7 @@ objfpy_repr (PyObject *self_)
     return PyString_FromString ("<gdb.Objfile (invalid)>");
 
   return PyString_FromFormat ("<gdb.Objfile filename=%s>",
-			      objfile_filename (obj));
+			      objfile_name (obj));
 }
 
 /* Subroutine of gdbpy_lookup_objfile_by_build_id to simplify it.

gdb/testsuite/gdb.base/jit-reader.exp

@@ -227,6 +227,16 @@ proc jit_reader_test {} {
 		    "Attempt to assign to an unmodifiable value\." \
 		    "cannot assign to register"
 	    }
+
+	    if { ![skip_python_tests] } {
+		gdb_test "python print(gdb.objfiles())" \
+		    "$any<gdb.Objfile filename=<< JIT compiled code >>>$any" \
+		    "python gdb.Objfile.__repr__ ()"
+
+		gdb_test "python print(list(map(lambda objf : objf.filename, gdb.objfiles())))" \
+		    "$any'<< JIT compiled code >>'$any" \
+		    "python gdb.Objfile.filename"
+	    }
 	}
     }