llvm-18-linker-tools does not include LLVMgold.so

[Paul Meckel]

Unlike all other llvm-*-linker-tools packages, this one does not install `/usr/lib/llvm-18/lib/LLVMgold.so`. It does however install a broken symlink to it at `/usr/lib/bfd-plugins/LLVMgold-18.so`
This results in compilation failures with clang++ when used with the `-flto` flag for link time optimization.

To reproduce:

main.cpp:
```c++
int main() { return 0; }
```

```bash
clang++ -flto main.cpp -o main
```

Results in:
```
/usr/bin/ld: /usr/lib/llvm-18/bin/../lib/LLVMgold.so: error loading plugin: /usr/lib/llvm-18/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
```

Package version is

llvm-18-linker-tools/noble,now 1:18.1.3-1 amd64

llvm-18-linker-tools:
  Installed: 1:18.1.3-1
  Candidate: 1:18.1.3-1
  Version table:
 *** 1:18.1.3-1 500
        500 http://de.archive.ubuntu.com/ubuntu noble/universe amd64 Packages
        100 /var/lib/dpkg/status

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Gianfranco Costamagna (costamagnagianfranco)]

Oracular is not really fixed, llvmGOLD.so is still not built on riscv64.

[Shengjing Zhu (zhsj)]

> llvmGOLD.so is still not built on riscv64

It's not been built from previous versions on riscv64 as well. So at least not a regression.

[Matthias Klose (doko)]

gold is not support upstream on riscv64