Launch.json dosnt contain svd_path

I have created two board files one for a atsamC21 and one for an atsamD10

The svd file for the samC21 I use is the existing samD21xxxx.SVD file , and the launch.json has the svd_path included and the debugger therefore shows the peripheral information

The other board file ( created 6 months later ) didnt have a suitable svd so I used the one from microchip device family pack and placed it in the misc/svd dir

The entry in the board file ie the svd_path was updated

But the launch.jason file never gets built with the svd_path line , if I add it manually , its works correctly , but of course on the IDE re-load its rebuilt and lost

I must be missing something but i cant see it , any ideas ( whats builds the launch.json: file