try_compile: Update documentation for other propagated variables

Help/command/try_compile.rst

@@ -102,6 +102,10 @@ default values:
 
 * :variable:`CMAKE_LINK_SEARCH_START_STATIC`
 * :variable:`CMAKE_LINK_SEARCH_END_STATIC`
+* :variable:`CMAKE_POSITION_INDEPENDENT_CODE`
+
+If :policy:`CMP0056` is set to ``NEW``, then
+:variable:`CMAKE_EXE_LINKER_FLAGS` is passed in as well.
 
 Set the :variable:`CMAKE_TRY_COMPILE_CONFIGURATION` variable to choose
 a build configuration.

Help/variable/CMAKE_POSITION_INDEPENDENT_CODE.rst

@@ -1,8 +1,9 @@
 CMAKE_POSITION_INDEPENDENT_CODE
 -------------------------------
 
-Default value for POSITION_INDEPENDENT_CODE of targets.
+Default value for :prop_tgt:`POSITION_INDEPENDENT_CODE` of targets.
 
-This variable is used to initialize the POSITION_INDEPENDENT_CODE
-property on all the targets.  See that target property for additional
-information.
+This variable is used to initialize the
+:prop_tgt:`POSITION_INDEPENDENT_CODE` property on all the targets.
+See that target property for additional information.  If set, it's
+value is also used by the :command:`try_compile` command.