Add deprecation warnings for policies CMP0120 and below

The OLD behaviors of all policies are deprecated, but only by
documentation.  Add an explicit deprecation diagnostic for policies
introduced in CMake 3.20 and below to encourage projects to port
away from setting policies to OLD.

1 files changed, 10 insertions, 1 deletions

diff --git a/Tests/RunCMake/CMP0115/CMP0115-OLD-stderr.txt b/Tests/RunCMake/CMP0115/CMP0115-OLD-stderr.txt
index 67d00f7..3472f33 100644
--- a/Tests/RunCMake/CMP0115/CMP0115-OLD-stderr.txt
+++ b/Tests/RunCMake/CMP0115/CMP0115-OLD-stderr.txt
@@ -1,4 +1,13 @@
-^CMake Error at CMP0115\.cmake:[0-9]+ \(add_executable\):
+^CMake Deprecation Warning at CMakeLists\.txt:[0-9]+ \(cmake_minimum_required\):
+  The OLD behavior for policy CMP0115 will be removed from a future version
+  of CMake\.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances\.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD\.
++
+CMake Error at CMP0115\.cmake:[0-9]+ \(add_executable\):
   Cannot find source file:
 
     noexist