Help: Add missing PCH_WARN_INVALID docs and related cleanups

Help/manual/cmake-properties.7.rst

@@ -128,7 +128,6 @@ Properties on Targets
    /prop_tgt/ARCHIVE_OUTPUT_DIRECTORY
    /prop_tgt/ARCHIVE_OUTPUT_NAME_CONFIG
    /prop_tgt/ARCHIVE_OUTPUT_NAME
-   /prop_tgt/PCH_WARN_INVALID
    /prop_tgt/AUTOGEN_BUILD_DIR
    /prop_tgt/AUTOGEN_ORIGIN_DEPENDS
    /prop_tgt/AUTOGEN_PARALLEL
@@ -312,6 +311,7 @@ Properties on Targets
    /prop_tgt/OSX_ARCHITECTURES
    /prop_tgt/OUTPUT_NAME_CONFIG
    /prop_tgt/OUTPUT_NAME
+   /prop_tgt/PCH_WARN_INVALID
    /prop_tgt/PDB_NAME_CONFIG
    /prop_tgt/PDB_NAME
    /prop_tgt/PDB_OUTPUT_DIRECTORY_CONFIG

Help/prop_tgt/PCH_WARN_INVALID.rst

@@ -2,7 +2,9 @@ PCH_WARN_INVALID
 ----------------
 
 When this property is set to true, the precompile header compiler options
-will contain a compiler flag wich should warn about invalid precompiled
+will contain a compiler flag which should warn about invalid precompiled
 headers e.g. ``-Winvalid-pch`` for GNU compiler.
 
-The defalut value is ``ON``.
+This property is initialized by the value of the
+:variable:`CMAKE_PCH_WARN_INVALID` variable if it is set when a target is
+created.  If that variable is not set, the property defaults to ``ON``.

Help/release/3.18.rst

@@ -117,6 +117,9 @@ Properties
 * The :prop_sf:`OBJECT_OUTPUTS` source file property now supports
   :manual:`generator expressions <cmake-generator-expressions(7)>`.
 
+* The :prop_tgt:`PCH_WARN_INVALID` target property was added to allow the
+  removal of the precompiled header invalid warning.
+
 * The :prop_tgt:`UNITY_BUILD_MODE` target property was added to tell
   generators which algorithm to use for grouping included source
   files.