CMP0022: Add unit test for null pointer check and message.

Tests/RunCMake/CMP0022/CMP0022-WARN-empty-old-result.txt

@@ -0,0 +1 @@
+0

Tests/RunCMake/CMP0022/CMP0022-WARN-empty-old-stderr.txt

@@ -0,0 +1,17 @@
+CMake Warning \(dev\) in CMakeLists.txt:
+  Policy CMP0022 is not set: INTERFACE_LINK_LIBRARIES defines the link
+  interface.  Run "cmake --help-policy CMP0022" for policy details.  Use the
+  cmake_policy command to set the policy and suppress this warning.
+
+  Target "bar" has a INTERFACE_LINK_LIBRARIES property which differs from its
+  LINK_INTERFACE_LIBRARIES properties.
+
+  INTERFACE_LINK_LIBRARIES:
+
+    foo
+
+  LINK_INTERFACE_LIBRARIES:
+
+    \(empty\)
+
+This warning is for project developers.  Use -Wno-dev to suppress it.

Tests/RunCMake/CMP0022/CMP0022-WARN-empty-old.cmake

@@ -0,0 +1,10 @@
+
+project(CMP0022-WARN-empty-old)
+
+add_library(foo SHARED empty_vs6_1.cpp)
+add_library(bar SHARED empty_vs6_2.cpp)
+
+set_property(TARGET bar PROPERTY INTERFACE_LINK_LIBRARIES foo)
+
+add_library(user empty.cpp)
+target_link_libraries(user bar)

Tests/RunCMake/CMP0022/RunCMakeTest.cmake

@@ -3,6 +3,7 @@ include(RunCMake)
 run_cmake(CMP0022-WARN)
 run_cmake(CMP0022-WARN-tll)
 run_cmake(CMP0022-WARN-static)
+run_cmake(CMP0022-WARN-empty-old)
 run_cmake(CMP0022-NOWARN-static)
 run_cmake(CMP0022-NOWARN-static-link_libraries)
 run_cmake(CMP0022-export)