add a lib for rendering text in sdl2 and rules to make in makefile

SDL2_ttf/cmake/FindSDL2main.cmake

@@ -0,0 +1,24 @@
+# FIXME: this should be provided by SDL2
+
+include(FindPackageHandleStandardArgs)
+include("${CMAKE_CURRENT_LIST_DIR}/CommonFindSDL2.cmake")
+
+find_library(SDL2_MAIN_LIBRARY
+    NAMES SDL2main
+    HINTS ${SDL2_DIR} ENV SDL2_DIR
+    PATH_SUFFIXES ${_lib_suffixes}
+)
+
+find_package_handle_standard_args(SDL2main
+    REQUIRED_VARS SDL2_MAIN_LIBRARY
+)
+
+if(SDL2main_FOUND)
+    if(NOT TARGET SDL2::SDL2main)
+        add_library(SDL2::SDL2main UNKNOWN IMPORTED)
+        set_target_properties(SDL2::SDL2main PROPERTIES
+            IMPORTED_LINK_INTERFACE_LANGUAGES "C"
+            IMPORTED_LOCATION "${SDL2_MAIN_LIBRARY}"
+        )
+    endif()
+endif()