Really slow compilation with large maps

Hello, I am experiencing a really slow compilation time with OneAPI 2024 on a single file which initializes some constant `unordered_map`s.

The source code is quite large (~4500 lines), so I just put it on [Compiler Explorer](https://godbolt.org/z/YzerMvh5Y).

The full command is this:
```bash
icpx -O1 -std=c++17 -fPIC -fno-fast-math -fsanitize=address,undefined -Wall -Wextra -pedantic -Wsign-conversion -Wfloat-conversion -Wfloat-equal -Wno-unknown-pragmas -Werror example.cpp -o example.x
```

Here are some compilation times measured with `time`.

OneAPI 2024.2.0.495:
```bash
real 16m51.163s
user 16m49.798s
sys 0m0.890s
```

OneAPI 2025.0.4.20:
```bash
real 15m40.380s
user 15m39.558s
sys 0m0.509s
```

clang++ 19.1.7:
```bash
real 0m39.850s
user 0m39.226s
sys 0m0.576s
```

I didn't measure the compilation time for g++ 14.2 but it surely is less than the time limit on Compiler Explorer as you can see [here](https://godbolt.org/z/Y43K8WT9G).

If it may be of any help, I also tried disabling optimizations and sanitizers and gathered these times:

| Flags | Time [s] |
|-------|----------|
| ` -O0` | ~12 |
| ` -O1` | ~47 |
| ` -O0 -fsanitize=address,undefined` | ~8 |

Start with the Compiler Explorer reproducer linked in the issue and run the full icpx command against the reported OneAPI versions. Compare the behavior with clang++ and the listed optimization and sanitizer combinations to narrow the trigger. Done should include a confirmed diagnosis and a measured improvement or clearly documented limitation for this case.

Written by the indexing model from the issue text.