[dev] Locally built Multipass picks up centrally installed Qt libs and crashes

**Describe the bug**
Locally built Multipass picks up centrally installed Qt libs instead of vcpkg ones and crashes. Stacktrace:

```
Thread 33 "QNetworkAccessM" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fff937fe6c0 (LWP 870434)]
0x00007ffff283089c in ?? () from /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
(gdb) where
#0 0x00007ffff283089c in ??? () at /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
#1 0x00007ffff2830b65 in ??? () at /usr/lib/x86_64-linux-gnu/qt6/plugins/tls/libqopensslbackend.so
#2 0x00007ffff7d7cd31 in QSslSocketPrivate::~QSslSocketPrivate() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#3 0x00007ffff7d7ce35 in QSslSocketPrivate::~QSslSocketPrivate() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#4 0x00007ffff7d6f3b5 in QSslSocket::~QSslSocket() () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#5 0x00007ffff7d15806 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#6 0x00007ffff7d15a35 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#7 0x00007ffff7d2518c in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#8 0x00007ffff7c7448e in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#9 0x00007ffff7c747f7 in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#10 0x00007ffff7d259bd in ??? () at /lib/x86_64-linux-gnu/libQt6Network.so.6
#11 0x00007ffff750f7b2 in QThreadStorageData::finish(void**) () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#12 0x00007ffff75028b0 in ??? () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#13 0x00007ffff75068f7 in ??? () at /lib/x86_64-linux-gnu/libQt6Core.so.6
#14 0x00007ffff6aa3d64 in start_thread (arg=) at ./nptl/pthread_create.c:448
#15 0x00007ffff6b373bc in __GI___clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78
```

There appears to be some sort of mismatch with respect to OpenSSL. There have been similar problems in the past; see https://github.com/canonical/multipass/pull/4529, which was replaced by https://github.com/canonical/multipass/pull/4530.

**To Reproduce**
Just follow build instructions (which install qt with `apt`) and attempt to run the daemon.

**Additional info**
- OS: Ubuntu 25.10
- CPU architecture or model: x86
- `multipass version`: 1.17.0-dev.1458+g7f143fd8

Start by following the issue's build instructions and launching the daemon, then inspect which Qt and OpenSSL libraries the locally built daemon and TLS plugin load. Review PRs #4529 and #4530 for prior context. Done means the daemon uses the vcpkg Qt dependencies consistently and no longer crashes on startup or TLS cleanup.

Written by the indexing model from the issue text.