Tic80 Arch build patch SDL2

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -163,6 +163,7 @@
 ################################
 # LUA
 ################################
+option(USE_SYSTEM_SDL2 "Use system-installed SDL2 instead of vendored" OFF)

 set(LUA_DIR ${THIRDPARTY_DIR}/lua)
 set(LUA_SRC
@@ -641,18 +642,27 @@
 ################################
 if(BUILD_SDL AND NOT EMSCRIPTEN AND NOT RPI)

-    if(WIN32)
-        set(HAVE_LIBC TRUE)
-    endif()
-
-    if(ANDROID)
-        include_directories(${ANDROID_NDK}/sources/android/cpufeatures)
-        set(SDL_STATIC_PIC ON CACHE BOOL "" FORCE)
-    endif()
-
-    set(SDL_SHARED OFF CACHE BOOL "" FORCE)
-
-    add_subdirectory(${THIRDPARTY_DIR}/sdl2)
+    if(USE_SYSTEM_SDL2)
+        find_package(SDL2 REQUIRED)
+        message(STATUS "Using system SDL2: ${SDL2_INCLUDE_DIRS}")
+        set(SDL2_LIB SDL2::SDL2)
+        set(SDL2_MAIN SDL2::SDL2main)
+    else()
+
+        if(WIN32)
+            set(HAVE_LIBC TRUE)
+        endif()
+
+        if(ANDROID)
+            include_directories(${ANDROID_NDK}/sources/android/cpufeatures)
+            set(SDL_STATIC_PIC ON CACHE BOOL "" FORCE)
+        endif()
+
+        set(SDL_SHARED OFF CACHE BOOL "" FORCE)
+
+        add_subdirectory(${THIRDPARTY_DIR}/sdl2)
+
+    endif()

 endif()

@@ -679,7 +689,7 @@
         target_link_options(player-sdl PRIVATE -static)
     endif()

-    target_link_libraries(player-sdl tic80core SDL2-static SDL2main)
+    target_link_libraries(player-sdl tic80core ${SDL2_LIB} ${SDL2_MAIN})
 endif()

 ################################
@@ -1228,7 +1238,7 @@
         elseif(RPI)
             target_link_libraries(tic80 libSDL2.a bcm_host)
         else()
-            target_link_libraries(tic80 SDL2-static)
+            target_link_libraries(tic80 ${SDL2_LIB})
         endif()
     endif()