Add SYSTEM target property

If it is ON, treat INTERFACE_INCLUDE_DIRECTORIES as system include directories.

Issue: #18040

Signed-off-by: Da Quexian <daquexian566@gmail.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/Help/prop_tgt/IMPORTED_NO_SYSTEM.rst b/Help/prop_tgt/IMPORTED_NO_SYSTEM.rst
index ee22d6f..49228ad 100644
--- a/Help/prop_tgt/IMPORTED_NO_SYSTEM.rst
+++ b/Help/prop_tgt/IMPORTED_NO_SYSTEM.rst
@@ -7,7 +7,8 @@ Specifies that an :ref:`Imported Target <Imported Targets>` is not
 a ``SYSTEM`` library.  This has the following effects:
 
 * Entries of :prop_tgt:`INTERFACE_INCLUDE_DIRECTORIES` are not treated
-  as ``SYSTEM`` include directories when compiling consumers, as they
+  as ``SYSTEM`` include directories when compiling consumers (regardless of
+  the value of the consumed target's :prop_tgt:`SYSTEM` property), as they
   would be by default.   Entries of
   :prop_tgt:`INTERFACE_SYSTEM_INCLUDE_DIRECTORIES` are not affected,
   and will always be treated as ``SYSTEM`` include directories.
diff --git a/Help/prop_tgt/SYSTEM.rst b/Help/prop_tgt/SYSTEM.rst
new file mode 100644
index 0000000..2db6aed
--- /dev/null
+++ b/Help/prop_tgt/SYSTEM.rst
@@ -0,0 +1,16 @@
+SYSTEM
+------
+
+.. versionadded:: 3.25
+
+Specifies that a target is a ``SYSTEM`` library.  This has the following effects:
+
+* Entries of :prop_tgt:`INTERFACE_INCLUDE_DIRECTORIES` are treated as ``SYSTEM``
+  include directories when compiling consumers.
+  Entries of :prop_tgt:`INTERFACE_SYSTEM_INCLUDE_DIRECTORIES` are not affected,
+  and will always be treated as ``SYSTEM`` include directories.
+
+For imported targets, this property has a default value `ON`, which means that their
+`INTERFACE_INCLUDE_DIRECTORIES` are treated as ``SYSTEM`` by default. If their
+`SYSTEM` property is `OFF`, then their `INTERFACE_INCLUDE_DIRECTORIES` will not be
+treated as ``SYSTEM``, regardless of the value of `IMPORTED_NO_SYSTEM` property.