the string is implicitly anchored, so "foo" does of course not match
"no-foo".

this allows us to de-noise the generated qfeatures.pri somewhat.

it still makes sense not to auto-include that file for performance
reasons, so this change is a functional no-op.

Change-Id: Ied75fd6459022c0b8c80843d62c4ab9eba9bf261
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>