Added a workaround for CMake versions prior 3.x.x.

Added a workaround for yesterday's commit regarding the unit tests and CMake
generator expressions. CMake versions prior 3.x.x do not understand $<CONFIG>
and require using $<CONFIGURATION>, which is in turn deprecated since 3.x.x.
Good thing this issue was totally not annoying.

CMake/dcmtkMacros.cmake

@@ -34,7 +34,7 @@ FUNCTION(DCMTK_ADD_TESTS MODULE)
             SET_PROPERTY(TEST "${TEST}" PROPERTY REQUIRED_FILES "${TEST_EXECUTABLE}")
         ENDFOREACH(TEST_LINE)
         ADD_CUSTOM_TARGET("${MODULE}-test-exhaustive"
-            COMMAND "${CMAKE_COMMAND}" "-DCONFIG=$<CONFIG>" "-P" "${DCMTK_SOURCE_DIR}/CMake/CTest/dcmtkCTestRunExhaustive.cmake"
+            COMMAND "${CMAKE_COMMAND}" "-DCONFIG=${DCMTK_CONFIG_GENERATOR_EXPRESSION}" "-P" "${DCMTK_SOURCE_DIR}/CMake/CTest/dcmtkCTestRunExhaustive.cmake"
             WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
         )
     ENDIF(BUILD_APPS AND DCMTK_RUN_CTEST_SCRIPT)

CMake/dcmtkPrepare.cmake

@@ -499,3 +499,13 @@ DCMTK_TEST_SOCKET_LIBRARY(socket "socket")
 IF(CMAKE_CXX_COMPILER_ID STREQUAL SunPro)
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -features=tmplrefstatic")
 ENDIF()
+
+#-----------------------------------------------------------------------------
+# workaround for using the deprecated generator expression $<CONFIGURATION>
+# with old CMake versions that do not understand $<CONFIG>
+#-----------------------------------------------------------------------------
+IF(CMAKE_VERSION VERSION_LESS 3.0.0)
+  SET(DCMTK_CONFIG_GENERATOR_EXPRESSION "$<CONFIGURATION>" CACHE INTERNAL "the generator expression to use for retriving the current config")
+ELSE()
+  SET(DCMTK_CONFIG_GENERATOR_EXPRESSION "$<CONFIG>" CACHE INTERNAL "the generator expression to use for retriving the current config")
+ENDIF()

CMakeLists.txt

@@ -69,7 +69,7 @@ ELSE(CMAKE_CROSSCOMPILING)
 ENDIF(CMAKE_CROSSCOMPILING)
 # Add a target to run the unit tests in exhaustive mode
 ADD_CUSTOM_TARGET("test-exhaustive"
-    COMMAND "${CMAKE_COMMAND}" "-DCONFIG=$<CONFIG>" "-P"
+    COMMAND "${CMAKE_COMMAND}" "-DCONFIG=${DCMTK_CONFIG_GENERATOR_EXPRESSION}" "-P"
         "${DCMTK_SOURCE_DIR}/CMake/CTest/dcmtkCTestRunExhaustive.cmake"
     WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
 )