"run test under cursor" can build wrong target

There is a small glitch with "run test under cursor": before running the test, qtcreator will perform a build.

current behaviour: qtcreator will do a build according to the "build steps" configuration. e.g. it will build the "all" target or the "current executable"

a potentially better default would be to build the target that is associated with the "test under cursor". this would prevent the test be run on a potentially outdated executable