FIX: interface deps under cmake < 3.3

cmake/external/any.cmake

@@ -17,8 +17,15 @@ ExternalProject_Add(
     TEST_COMMAND      ""
 )
 
-ADD_LIBRARY(lib_any INTERFACE)
-ADD_DEPENDENCIES(lib_any extern_lib_any)
+if (${CMAKE_VERSION} VERSION_LESS "3.3.0")
+    set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/lib_any_dummy.c)
+    file(WRITE ${dummyfile} "const char * dummy_any = \"${dummyfile}\";")
+    add_library(lib_any STATIC ${dummyfile})
+else()
+    add_library(lib_any INTERFACE)
+endif()
+
+add_dependencies(lib_any extern_lib_any)
 
 add_definitions(-DANY_IMPL_ANY_CAST_MOVEABLE)
-LIST(APPEND external_project_dependencies extern_lib_any)
+LIST(APPEND external_project_dependencies lib_any)

cmake/external/eigen.cmake

@@ -26,7 +26,14 @@ ExternalProject_Add(
     TEST_COMMAND      ""
 )
 
-ADD_LIBRARY(eigen3 INTERFACE)
-ADD_DEPENDENCIES(eigen3 extern_eigen3)
+if (${CMAKE_VERSION} VERSION_LESS "3.3.0")
+    set(dummyfile ${CMAKE_CURRENT_BINARY_DIR}/eigen3_dummy.c)
+    file(WRITE ${dummyfile} "const char * dummy_eigen3 = \"${dummyfile}\";")
+    add_library(eigen3 STATIC ${dummyfile})
+else()
+    add_library(eigen3 INTERFACE)
+endif()
 
-LIST(APPEND external_project_dependencies extern_eigen3)
+add_dependencies(eigen3 extern_eigen3)
+
+LIST(APPEND external_project_dependencies eigen3)