Enable Java test more carefully on Apple

The CTEST_RUN_Java option added by commit c8f39193 (Avoid problem
reading jni.h on Macs, 2010-10-25) was a quick hack to disable the Java
test on Mac machines after an update from Apple created a broken jni.h
symlink.  Remove the option and instead test whether jni.h exists as a
readable file before reading it.  This restores the original Java test
enabling logic but makes it robust to the broken symlink.

Tests/CMakeLists.txt

@@ -1868,22 +1868,13 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
     ENDIF()
   ENDIF()
 
-  if(NOT DEFINED CTEST_RUN_Java)
-    if(APPLE)
-      set(CTEST_RUN_Java OFF)
-    else()
-      set(CTEST_RUN_Java ON)
-    endif()
-  endif()
-
-  IF(CTEST_RUN_Java)
   find_package(Java QUIET)
   IF(JAVA_COMPILE AND JAVA_RUNTIME AND JAVA_ARCHIVE AND NOT MINGW)
     GET_FILENAME_COMPONENT(JNIPATH ${JAVA_COMPILE} PATH)
     FIND_FILE(JNI_H jni.h
       "${JNIPATH}/../include"
       "${JNIPATH}/../java/include")
-      IF(JNI_H)
+    IF(JNI_H AND EXISTS "${JNI_H}") # in case jni.h is a broken symlink
       FILE(READ "${JNI_H}" JNI_FILE)
       IF("${JNI_FILE}" MATCHES "JDK1_2")
         ADD_TEST(Java ${CMAKE_CTEST_COMMAND}
@@ -1898,9 +1889,8 @@ ${CMake_BINARY_DIR}/bin/cmake -DVERSION=master -P ${CMake_SOURCE_DIR}/Utilities/
           --test-command ${JAVA_RUNTIME} -classpath hello.jar HelloWorld)
         LIST(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/Java")
       ENDIF("${JNI_FILE}" MATCHES "JDK1_2")
-      ENDIF(JNI_H)
+    ENDIF()
   ENDIF(JAVA_COMPILE AND JAVA_RUNTIME AND JAVA_ARCHIVE AND NOT MINGW)
-  ENDIF(CTEST_RUN_Java)
 
   # add some cross compiler tests, for now only with makefile based generators
   IF(CMAKE_TEST_GENERATOR MATCHES "Makefiles" OR CMAKE_TEST_GENERATOR MATCHES "KDevelop")