Fix tool on different platforms.

tools/assetstool/CMakeLists.txt

@@ -12,6 +12,9 @@ add_custom_target(dawnassets
     --input=${DAWN_ASSETS_BUILD_DIR}
     --output=${DAWN_BUILD_DIR}/dawn.tar
   COMMENT "Bundling assets..."
-    USES_TERMINAL
-    DEPENDS ${DAWN_ASSETS}
+  USES_TERMINAL
+  DEPENDS
+    ${DAWN_ASSETS}
+    ${DAWN_TOOLS_DIR}/assetstool/assetstool.py
+    ${Python3_EXECUTABLE}
 )

tools/assetstool/assetstool.py

@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 # Copyright (c) 2023 Dominic Masters
 # 
 # This software is released under the MIT License.