Merge bitcoin#15127: docs: Clarifying testing instructions

ef5ebc6 docs: Clarifying testing instructions (benthecarman)

Pull request description:

  This statement confused me on my first time reading through.  Hopefully, this addition will help someone else on their first time.

Tree-SHA512: 17f421275adb7586eca954910269d29fcd3bacc42fab4bc2e01110f9e13ca6f8c1ca178246f7192e1131f14ced7f7dc0b57e7aec324898807c1813a2ebc513de

test/README.md

@@ -17,7 +17,8 @@ request is opened. Both sets of tests can also be run locally.
 
 # Running tests locally
 
-Build for your system first. Be sure to enable wallet, utils and daemon when you configure. Tests will not run otherwise.
+Before tests can be run locally, Bitcoin Core must be built.  See the [building instructions](/doc#building) for help.
+
 
 ### Functional tests