fix "cmake -DWITH_PCRE=bundled"

after building with system

cmake/pcre.cmake

@@ -5,7 +5,7 @@ MACRO (CHECK_PCRE)
   IF(WITH_PCRE STREQUAL "system" OR WITH_PCRE STREQUAL "auto")
     CHECK_LIBRARY_EXISTS(pcre pcre_stack_guard "" HAVE_PCRE)
   ENDIF()
-  IF(NOT HAVE_PCRE)
+  IF(NOT HAVE_PCRE OR WITH_PCRE STREQUAL "bundled")
     IF (WITH_PCRE STREQUAL "system")
       MESSAGE(FATAL_ERROR "system pcre is not found or unusable")
     ENDIF()