Add new target-property `IMPORTED_GLOBAL`.

The purpose of this new `IMPORTED_GLOBAL` target-property is to prolong
the lifetime and scope of `IMPORTED` targets in such a way as if they
had been created with the keyword `GLOBAL` in the first place.

* It can only be set to `TRUE`. That means, a local `IMPORTED` target
  can be promoted to global scope but a global `IMPORTED` target cannot
  be degraded to local scope!
* Setting it to `TRUE` only succeeds if done from within the same
  directory in which the `IMPORTED` target was created in the first
  place.

Fixes #17256.

1 files changed, 15 insertions, 0 deletions

diff --git a/Help/release/dev/imported-promotion.rst b/Help/release/dev/imported-promotion.rst
new file mode 100644
index 0000000..d184178
--- /dev/null
+++ b/Help/release/dev/imported-promotion.rst
@@ -0,0 +1,15 @@
+imported-promotion
+------------------
+
+* Added new target-property :prop_tgt:`IMPORTED_GLOBAL` which
+  indicates if an :ref:`IMPORTED target <Imported Targets>` is
+  globally visible.
+  It will be set automatically if such an imported target is
+  created with the ``GLOBAL`` flag.
+
+* Additionally, it is now also possible to promote a local imported
+  target to become globally visible by setting its
+  :prop_tgt:`IMPORTED_GLOBAL` property to `TRUE`. (However, this
+  promotion can only succeed if it is done from within the same
+  directory where the imported target was created in the first
+  place.) Setting it to `FALSE` is not supported!