Add test that CMake errors with empty libs

When the library language cannot be determined, make sure CMake errors,
not segfaults (bug #11230)

Tests/CMakeLists.txt

@@ -153,6 +153,9 @@ IF(BUILD_TESTING)
   ADD_TEST_MACRO(ExportImport ExportImport)
   ADD_TEST_MACRO(Unset Unset)
   ADD_TEST_MACRO(PolicyScope PolicyScope)
+  ADD_TEST_MACRO(EmptyLibrary EmptyLibrary)
+  SET_TESTS_PROPERTIES(EmptyLibrary PROPERTIES
+    PASS_REGULAR_EXPRESSION "CMake Error: Cannot determine link language for target \"test\"")
   ADD_TEST_MACRO(CrossCompile CrossCompile)
   SET_TESTS_PROPERTIES(CrossCompile PROPERTIES
     PASS_REGULAR_EXPRESSION "TRY_RUN.. invoked in cross-compiling mode")

Tests/EmptyLibrary/CMakeLists.txt

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 2.6)
+project(TestEmptyLibrary)
+
+add_subdirectory(subdir)

Tests/EmptyLibrary/subdir/CMakeLists.txt

@@ -0,0 +1 @@
+add_library(test test.h)

Tests/EmptyLibrary/subdir/test.h

@@ -0,0 +1 @@
+extern int dummy;