test-cases harness: refresh just before update()

This makes it so that in a -Dsingle-threaded build of test-cases, if a
crash happens, the test case name will be printed just before the stderr
of the crash.

src/test.zig

@@ -1594,6 +1594,7 @@ pub const TestContext = struct {
 
             var module_node = update_node.start("parse/analysis/codegen", 0);
             module_node.activate();
+            module_node.context.refresh();
             try comp.makeBinFileWritable();
             try comp.update();
             module_node.end();