Help: Add note about restoring pre-3.0 link libraries genex behavior

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diff --git a/Help/release/dev/note-link-libraries-genex.rst b/Help/release/dev/note-link-libraries-genex.rst
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+note-link-libraries-genex
+-------------------------
+
+* In CMake 3.0 the :command:`target_link_libraries` command
+  accidentally began allowing unquoted arguments to use
+  :manual:`generator expressions <cmake-generator-expressions(7)>`
+  containing a (``;`` separated) list within them.  For example::
+
+    set(libs B C)
+    target_link_libraries(A PUBLIC $<BUILD_INTERFACE:${libs}>)
+
+  This is equivalent to writing::
+
+    target_link_libraries(A PUBLIC $<BUILD_INTERFACE:B C>)
+
+  and was never intended to work.  It did not work in CMake 2.8.12.
+  Such generator expressions should be in quoted arguments::
+
+    set(libs B C)
+    target_link_libraries(A PUBLIC "$<BUILD_INTERFACE:${libs}>")
+
+  CMake 3.1 again requires the quotes for this to work correctly.