Let us start here, from square one. No, from Zero!

external/imgui/CMakeLists.txt

@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.9)
+project(imgui CXX)
+
+# dear imgui uses the C++ virtual interfaces for DirectX
+remove_definitions(-DCINTERFACE)
+
+set(IMGUI_HEADERS
+        imconfig.h
+        imgui.h
+        imgui_internal.h
+)
+set(IMGUI_SOURCES
+        imgui.cpp
+        imgui_draw.cpp
+        imgui_tables.cpp
+        imgui_widgets.cpp
+        imgui_demo.cpp
+)
+
+add_library(imgui STATIC ${IMGUI_HEADERS} ${IMGUI_SOURCES})
+target_include_directories(imgui PRIVATE ${PROJECT_SOURCE_DIR})