overlappingschwarztest: remove broken runtime check and fix missing return value
- The test does not compile if either SuperLU or SuiteSparse are not present. The reason is a check that assumes that the corresponding macros are defined to
falsewhile they are in fact undefined.
testfunction is missing a return statement if neither of the libs is found.
However, the original commit message of e5ead46f does not fit exactly: In master the test is guarded in CMakeLists.txt which makes this check useless. But since guarding the test in CMake is more invasive, simply disabling the broken check in the test is IMO the preferred fix.