BUG: Only test for cxx flags the first time around

Modules/TestCXXAcceptsFlag.cmake

@@ -7,21 +7,23 @@
 #
 
 MACRO(CHECK_CXX_ACCEPTS_FLAG FLAGS  VARIABLE)
-  MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS}")
-  TRY_COMPILE(${VARIABLE}
-    ${CMAKE_BINARY_DIR}
-    ${CMAKE_ROOT}/Modules/DummyCXXFile.cxx
-    CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${FLAGS}
-    OUTPUT_VARIABLE OUTPUT) 
-  IF(${VARIABLE})
-    MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS} - yes")
-    FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeOutput.log
-      "Determining if the CXX compiler accepts the flag ${FLAGS} passed with "
-      "the following output:\n${OUTPUT}\n\n")
-  ELSE(${VARIABLE})
-    MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS} - no")
-    FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeError.log
-      "Determining if the CXX compiler accepts the flag ${FLAGS} failed with "
-      "the following output:\n${OUTPUT}\n\n")
-  ENDIF(${VARIABLE})
+  IF(DEFINED ${VARIABLE})
+    MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS}")
+    TRY_COMPILE(${VARIABLE}
+      ${CMAKE_BINARY_DIR}
+      ${CMAKE_ROOT}/Modules/DummyCXXFile.cxx
+      CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${FLAGS}
+      OUTPUT_VARIABLE OUTPUT) 
+    IF(${VARIABLE})
+      MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS} - yes")
+      FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeOutput.log
+        "Determining if the CXX compiler accepts the flag ${FLAGS} passed with "
+        "the following output:\n${OUTPUT}\n\n")
+    ELSE(${VARIABLE})
+      MESSAGE(STATUS "Checking to see if CXX compiler acepts flag ${FLAGS} - no")
+      FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeError.log
+        "Determining if the CXX compiler accepts the flag ${FLAGS} failed with "
+        "the following output:\n${OUTPUT}\n\n")
+    ENDIF(${VARIABLE})
+  ENDIF(DEFINED ${VARIABLE})
 ENDMACRO(CHECK_CXX_ACCEPTS_FLAG)