Merge branch 'doc-pkgconfig-list' into release-3.9

Modules/FindPkgConfig.cmake

@@ -65,7 +65,7 @@ macro(_pkgconfig_invoke _pkglist _prefix _varname _regexp)
     set(_pkgconfig_${_varname} "")
     _pkgconfig_unset(${_prefix}_${_varname})
   else()
-    string(REGEX REPLACE "[\r\n]"                  " " _pkgconfig_invoke_result "${_pkgconfig_invoke_result}")
+    string(REGEX REPLACE "[\r\n]"       " " _pkgconfig_invoke_result "${_pkgconfig_invoke_result}")
 
     if (NOT ${_regexp} STREQUAL "")
       string(REGEX REPLACE "${_regexp}" " " _pkgconfig_invoke_result "${_pkgconfig_invoke_result}")
@@ -86,6 +86,9 @@ endmacro()
 
     pkg_get_variable(<RESULT> <MODULE> <VARIABLE>)
 
+  If multiple values are returned variable will contain a
+  :ref:`;-list <CMake Language Lists>`.
+
   For example:
 
   .. code-block:: cmake
@@ -524,6 +527,9 @@ endmacro()
     <XPREFIX> = <PREFIX>        for common case
     <XPREFIX> = <PREFIX>_STATIC for static linking
 
+ Every variable containing multiple values will be a
+ :ref:`;-list <CMake Language Lists>`.
+
  There are some special variables whose prefix depends on the count of
  given modules.  When there is only one module, <PREFIX> stays
  unchanged.  When there are multiple modules, the prefix will be