Spindle changes library search behavior, causes libmpi to not be found

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In the Ubuntu 24.04 images used for CI, if MPICH is installed but `ldconfig` is not run to update the cache, MPI applications will run successfully without Spindle, but with Spindle at level medium or high, libmpi is not found:

```
./mpi-hello: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory
```

`LD_DEBUG=all` output without Spindle, `ldconfig` not run:

```
file=libmpi.so.12 [0]; needed by /shared/examples/./mpi-hello [0]
find library=libmpi.so.12 [0]; searching
search path=/usr/lib/glibc-hwcaps/x86-64-v3:/usr/lib/glibc-hwcaps/x86-64-v2:/usr/lib (system search path)
trying file=/usr/lib/glibc-hwcaps/x86-64-v3/libmpi.so.12
trying file=/usr/lib/glibc-hwcaps/x86-64-v2/libmpi.so.12
trying file=/usr/lib/libmpi.so.12

file=libmpi.so.12 [0]; generating link map
dynamic: 0x000077e828e7c8c0 base: 0x000077e8263d5000 size: 0x0000000002ea1d10
entry: 0x000077e8263d5000 phdr: 0x000077e8263d5040 phnum: 12
```

With Spindle, `ldconfig` run:

```
file=libmpi.so.12 [0]; needed by ./mpi-hello [0]
find library=libmpi.so.12 [0]; searching
search path=/usr/lib/glibc-hwcaps/x86-64-v3:/usr/lib/glibc-hwcaps/x86-64-v2:/usr/lib (system search path)
trying file=/usr/lib/glibc-hwcaps/x86-64-v3/libmpi.so.12
trying file=/__not_exglibc-hwcaps/x86-64-v2/libmpi.so.12
trying file=/__not_exlibmpi.so.12
search cache=/etc/ld.so.cache
trying file=/usr/lib/libmpi.so.12

file=libmpi.so.12 [0]; generating link map
dynamic: 0x00007a2974da58c0 base: 0x00007a29722fe000 size: 0x0000000002ea1d10
entry: 0x00007a29722fe000 phdr: 0x00007a29722fe040 phnum: 12
```

While libmpi.so.12 is found in the cache, this behavior is already different from the non-Spindle case, which finds libmpi.so.12 _prior_ to searching the cache.

With Spindle, `ldconfig` not run, failing case:

```
file=libmpi.so.12 [0]; needed by ./mpi-hello [0]
find library=libmpi.so.12 [0]; searching
search path=/usr/lib/glibc-hwcaps/x86-64-v3:/usr/lib/glibc-hwcaps/x86-64-v2:/usr/lib (system search path)
trying file=/usr/lib/glibc-hwcaps/x86-64-v3/libmpi.so.12
trying file=/__not_exglibc-hwcaps/x86-64-v2/libmpi.so.12
trying file=/__not_exlibmpi.so.12
search cache=/etc/ld.so.cache
search path=/lib/x86_64-linux-gnu:/usr/lib/x86_64-linux-gnu/glibc-hwcaps/x86-64-v3:/usr/lib/x86_64-linux-gnu/glibc-hwcaps/x86-64-v2:/usr/lib/x8-gnu:/lib/hwcaps/x86-64-v3:/lib/glibc-hwcaps/x86-64-v2:/lib (system search path)
trying file=/lib/x86_64-linux-gnu/libmpi.so.12
trying file=/usr/lib/x86_64-linux-gnu/glibc-hwcaps/x86-64-v3/libmpi.so.12
trying file=/__not_exists/4-linux-gnu/glibc-hwcaps/x86-64-v2/libmpi.so.12
trying file=/__not_exists/4-linux-gnu/libmpi.so.12
trying file=/lib/glibc-hwcaps/x86-64-v3/libmpi.so.12
trying file=/__noglibc-hwcaps/x86-64-v2/libmpi.so.12
trying file=/__nolibmpi.so.12

./mpi-hello: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory
```

Here, `/usr/lib` doesn't get searched at all.

Reproduce the issue in the Ubuntu 24.04 CI environment with MPICH, comparing MPI loading with Spindle disabled and at medium or high level. Start with the `mpi-hello` executable and the supplied `LD_DEBUG=all` traces, especially the `/usr/lib` and `/etc/ld.so.cache` searches. Done means Spindle no longer prevents `libmpi.so.12` from being found when `ldconfig` has not been run.

Written by the indexing model from the issue text.