FIX: Trying to fix CI on Windows

CMakeLists.txt

@@ -16,7 +16,7 @@ include(ProcessorCount)
 ProcessorCount(N_CORES)
 if(N_CORES GREATER 1)
     math(EXPR N_CORES "${N_CORES}-1")
-    set(CTEST_BUILD_FLAGS -j${N_CORES})
+    set(CTEST_BUILD_FLAGS -j ${N_CORES})
     set(ENV{N_CORES} ${N_CORES})
     set(ctest_test_args ${ctest_test_args} PARALLEL_LEVEL ${N_CORES})
 endif()