BUG: fix for bug 6117 pkgconfig

Modules/FindPkgConfig.cmake

@@ -317,12 +317,12 @@ endmacro(_pkg_check_modules_internal)
 ###
 macro(pkg_check_modules _prefix _module0)
   # check cached value
-  if (NOT DEFINED __pkg_config_checked_${_prefix} OR __pkg_config_checked_${_prefix} LESS ${PKG_CONFIG_VERSION})
+  if (NOT DEFINED __pkg_config_checked_${_prefix} OR __pkg_config_checked_${_prefix} LESS ${PKG_CONFIG_VERSION} OR NOT ${_prefix}_FOUND)
     _pkgconfig_parse_options   (_pkg_modules _pkg_is_required "${_module0}" ${ARGN})
     _pkg_check_modules_internal("${_pkg_is_required}" 0 "${_prefix}" ${_pkg_modules})
 
     _pkgconfig_set(__pkg_config_checked_${_prefix} ${PKG_CONFIG_VERSION})
-  endif(NOT DEFINED __pkg_config_checked_${_prefix} OR __pkg_config_checked_${_prefix} LESS ${PKG_CONFIG_VERSION})
+  endif(NOT DEFINED __pkg_config_checked_${_prefix} OR __pkg_config_checked_${_prefix} LESS ${PKG_CONFIG_VERSION} OR NOT ${_prefix}_FOUND)
 endmacro(pkg_check_modules)
 
 ###