[cmake] Remove line breaks in string

Line breaks are not allowed in cmake strings. After
version 3.0 linebreaking with backslash is possible.

test/common/generalproblem/CMakeLists.txt

@@ -5,27 +5,21 @@ add_dumux_test(test_general_box test_general test_generalproblem2p.cc
                  --script fuzzy
                  --files ${CMAKE_SOURCE_DIR}/test/references/generallens_box-reference.vtu
                          ${CMAKE_CURRENT_BINARY_DIR}/generallens_box-00003.vtu
-                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general
-                            -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input
-                            -ModelType Box")
+                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input -ModelType Box")
 
 add_dumux_test(test_general_cc test_general test_generalproblem2p.cc
                python ${CMAKE_SOURCE_DIR}/bin/runtest.py
                  --script fuzzy
                  --files ${CMAKE_SOURCE_DIR}/test/references/generallens_cc-reference.vtu
                          ${CMAKE_CURRENT_BINARY_DIR}/generallens_cc-00003.vtu
-                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general
-                            -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input
-                            -ModelType CC")
+                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input -ModelType CC")
 
 add_dumux_test(test_general_dec test_general test_generalproblem2p.cc
                python ${CMAKE_SOURCE_DIR}/bin/runtest.py
                  --script fuzzy
                  --files ${CMAKE_SOURCE_DIR}/test/references/generallens_decoupled-reference.vtu
                          ${CMAKE_CURRENT_BINARY_DIR}/generallens_decoupled-00003.vtu
-                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general
-                            -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input
-                            -ModelType Decoupled")
+                 --command "${CMAKE_CURRENT_BINARY_DIR}/test_general -ParameterFile ${CMAKE_CURRENT_SOURCE_DIR}/test_generalproblem2p_reference.input -ModelType Decoupled")
 
 #install sources
 install(FILES