Add 'tests' definition.
    
    Defining this option will iimit the tests performed with the "--with testsuite"
    option:
    
    $ rpmbuild -bb --with testsuite --define 'tests "gdb.base/break.exp gdb.dwarf2/*.exp"' \
       gdb.spec
    
    The above will build the RPM with testing, but it will only test the listed tests
    (just as if they were passed to TESTS="gdb.base/break.exp gdb.dwarf2/*.exp").