umr needs a rebuild for SteamOS 3.6

[matte-schwartz]

Your system information

• Steam client version: 1729208001
• SteamOS version: 3.6.18
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes, Preview
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

installing umr from the repo and trying to use it results in:

(deck@steamdeck ~)$ umr
umr: error while loading shared libraries: libLLVM-15.so: cannot open shared object file: No such file or directory