Pin version Emscripten SDK to latest known to work

Fixes:

```
wasm-ld: error: duplicate symbol: pthread_kill

>>> defined in /opt/opend/bin/../xpacks/opend-latest-xpack-emscripten/lib/libdruntime-ldc.a(osthread.o)
>>> defined in /opt/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/libc-debug.a(library_pthread_stub.o)
```

Author: 0xEAB

definitions/containerfiles.ini

@@ -590,6 +590,7 @@ level = false
 [opend:ci]
 level = 2.106.1
 extras[zig] = 0.16.0
+env[EMSDK_VERSION] = 5.0.5
 
 [ldc-xtensa:1.39.0]
 level = 2.109.1