Help: Fix small typos in documentation

Help/variable/CMAKE_LINK_SEARCH_END_STATIC.rst

@@ -15,7 +15,7 @@ back to its starting type.  This property switches the final linker
 search type to ``-Bstatic`` regardless of how it started.
 
 This variable is used to initialize the target property
-:prop_tgt:`LINK_SEARCH_END_STATIC` for all targets. If set, it's
+:prop_tgt:`LINK_SEARCH_END_STATIC` for all targets. If set, its
 value is also used by the :command:`try_compile` command.
 
 See also :variable:`CMAKE_LINK_SEARCH_START_STATIC`.

Help/variable/CMAKE_LINK_SEARCH_START_STATIC.rst

@@ -16,7 +16,7 @@ when linking an executable statically (e.g.  with the GNU ``-static``
 option).
 
 This variable is used to initialize the target property
-:prop_tgt:`LINK_SEARCH_START_STATIC` for all targets.  If set, it's
+:prop_tgt:`LINK_SEARCH_START_STATIC` for all targets.  If set, its
 value is also used by the :command:`try_compile` command.
 
 See also :variable:`CMAKE_LINK_SEARCH_END_STATIC`.

Help/variable/CMAKE_POSITION_INDEPENDENT_CODE.rst

@@ -5,5 +5,5 @@ Default value for :prop_tgt:`POSITION_INDEPENDENT_CODE` of targets.
 
 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
+See that target property for additional information.  If set, its
 value is also used by the :command:`try_compile` command.