fbt: Fixed build for users with space in username (#1437)

Co-authored-by: あく <alleteam@gmail.com>
Co-authored-by: hedger <hedger@users.noreply.github.com>

assets/SConscript

@@ -97,7 +97,7 @@ if assetsenv["IS_BASE_FIRMWARE"]:
         "#/assets/resources/Manifest",
         assetsenv.GlobRecursive("*", "resources", exclude="Manifest"),
         action=Action(
-            '${PYTHON3} ${ASSETS_COMPILER} manifest "${TARGET.dir.posix}"',
+            '${PYTHON3} "${ASSETS_COMPILER}" manifest "${TARGET.dir.posix}"',
             "${RESMANIFESTCOMSTR}",
         ),
     )