Mention find_package(Trilinos ...) problem with undefined compilers (#…

…12104)

RELEASE_NOTES

@@ -25,13 +25,24 @@ CMake
 
     This may break people's existing configurations because it will install
     libs in `<prefix>/libs64/` instead of in `<prefix>/libs/` on many systems
-    (e.g. Linux systems).  To revert back to using `<prefix>/lib` but still
-    use `GNUInstallDirs.cmake` for Trilinos, set `-D
-    CMAKE_INSTALL_LIBDIR:STRING=lib`.  NOTE: The setting `-D
-    Trilinos_USE_GNUINSTALLDIRS=OFF` is deprecated and may be removed in the
-    future. (I.e. the usage of `GNUInstallDirs.cmake` may be hard-coded in the
-    future so please try adjusting to the usage of `GNUInstallDirs.cmake` by
-    Trilinos.)  See
+    (e.g. Linux systems).  For example, this will break downstream CMake
+    projects that call `find_package(Trilinos ...)` before defining the
+    compilers (e.g. so they can get the compilers from Trilinos).  If the
+    compilers are not defined, `find_package()` will not search
+    `<prefix>/lib64`.  To revert back to using `<prefix>/lib` but still use
+    `GNUInstallDirs.cmake` for Trilinos, set `-D
+    CMAKE_INSTALL_LIBDIR:STRING=lib` when configuring Trilinos.  To avoid the
+    `find_package(Trilinos ...)` problem not searching `<prefix>/lib64`,
+    consider explicitly specifying the compiler to and having the downstream
+    CMake project define the compilers first with `project(<ProjectName>
+    COMPILERS C CXX ...)` before calling `find_package(Trilinos ...)`.  (That
+    is, don't try to get the compilers from the installed Trilinos, see
+    https://github.com/trilinos/Trilinos/issues/12306.)
+
+    NOTE: The setting `-D Trilinos_USE_GNUINSTALLDIRS=OFF` is deprecated and
+    may be removed in the future. (I.e. the usage of `GNUInstallDirs.cmake`
+    may be hard-coded in the future so please try adjusting to the usage of
+    `GNUInstallDirs.cmake` by Trilinos.)  See
     https://github.com/trilinos/Trilinos/issues/12104#issuecomment-1691945033
     for additional details and instructions.