port: build: move to CMake

god forgive me

cmake/AssetUtils.cmake

@@ -0,0 +1,27 @@
+# execute a header generator (execcmd) for every json file in jsonpath, collect headers in headerlist
+# note that this reads ROMID
+macro(generate_asset_headers jsonpath execcmd extraarg headerlist)
+  set(TMP_JSON "")
+
+  if (${jsonpath} MATCHES "\.json")
+    # is a json file
+    list(APPEND TMP_JSON "${CMAKE_SOURCE_DIR}/${ASSET_DIR}/${jsonpath}")
+  else()
+    # is a directory
+    file(GLOB TMP_JSON "${CMAKE_SOURCE_DIR}/${ASSET_DIR}/${jsonpath}*.json")
+  endif()
+
+  foreach(JSON ${TMP_JSON})
+    unset(HEADERNAME)
+    string(REPLACE ".json" ".h" HEADERNAME ${JSON})
+    string(REPLACE "${CMAKE_SOURCE_DIR}/${ASSET_DIR}" "${CMAKE_BINARY_DIR}/${GENERATED_DIR}" HEADERNAME ${HEADERNAME})
+    add_custom_command(
+      OUTPUT  ${HEADERNAME}
+      DEPENDS ${JSON}
+      COMMAND ${execcmd} ${JSON} ${extraarg} --headers-only --romid=${ROMID}
+    )
+    list(APPEND ${headerlist} "${HEADERNAME}")
+  endforeach()
+
+  unset(TMP_JSON)
+endmacro()