Fix typo, and disable own dtrace proibes on Solaris, really.

cmake/dtrace.cmake

@@ -43,7 +43,7 @@ MACRO(CHECK_DTRACE)
  IF(DTRACE AND NOT CMAKE_SYSTEM_NAME MATCHES "FreeBSD"
      AND NOT BUGGY_GCC_NO_DTRACE_MODULES
      AND NOT BUGGY_LINUX_DTRACE
-     AND NOT SYSTEM_NAME MATCHES "SunOS")
+     AND NOT CMAKE_SYSTEM_NAME MATCHES "SunOS")
    SET(ENABLE_DTRACE ON CACHE BOOL "Enable dtrace")
  ENDIF()
  SET(HAVE_DTRACE ${ENABLE_DTRACE})