kwsysPlatformTests: Use if(DEFINED) to simplify conditions

Replace old hacks of the form 'if("${VAR}" MATCHES "^${VAR}$")'
with the much simpler 'if(NOT DEFINED ${VAR})'.

Change-Id: Ie0e2fc5ceb85156221abe8938dfdd148b3862742

kwsysPlatformTests.cmake

@@ -13,7 +13,7 @@ SET(KWSYS_PLATFORM_TEST_FILE_C kwsysPlatformTestsC.c)
 SET(KWSYS_PLATFORM_TEST_FILE_CXX kwsysPlatformTestsCXX.cxx)
 
 MACRO(KWSYS_PLATFORM_TEST lang var description invert)
-  IF("${var}_COMPILED" MATCHES "^${var}_COMPILED$")
+  IF(NOT DEFINED ${var}_COMPILED)
     MESSAGE(STATUS "${description}")
     TRY_COMPILE(${var}_COMPILED
       ${CMAKE_CURRENT_BINARY_DIR}
@@ -43,7 +43,7 @@ MACRO(KWSYS_PLATFORM_TEST lang var description invert)
         MESSAGE(STATUS "${description} - no")
       ENDIF(${var}_COMPILED)
     ENDIF(${invert} MATCHES INVERT)
-  ENDIF("${var}_COMPILED" MATCHES "^${var}_COMPILED$")
+  ENDIF()
   IF(${invert} MATCHES INVERT)
     IF(${var}_COMPILED)
       SET(${var} 0)
@@ -60,7 +60,7 @@ MACRO(KWSYS_PLATFORM_TEST lang var description invert)
 ENDMACRO(KWSYS_PLATFORM_TEST)
 
 MACRO(KWSYS_PLATFORM_TEST_RUN lang var description invert)
-  IF("${var}" MATCHES "^${var}$")
+  IF(NOT DEFINED ${var})
     MESSAGE(STATUS "${description}")
     TRY_RUN(${var} ${var}_COMPILED
       ${CMAKE_CURRENT_BINARY_DIR}
@@ -107,7 +107,7 @@ MACRO(KWSYS_PLATFORM_TEST_RUN lang var description invert)
         MESSAGE(STATUS "${description} - failed to compile")
       ENDIF(${var}_COMPILED)
     ENDIF(${invert} MATCHES INVERT)
-  ENDIF("${var}" MATCHES "^${var}$")
+  ENDIF()
 
   IF(${invert} MATCHES INVERT)
     IF(${var}_COMPILED)