Compile bug: vulkan-shaders-gen is installed into the build location instead of $PREFIX/bin/vulkan-shaders-gen

### Git commit

5664

### Operating systems

BSD

### GGML backends

CPU

### Problem description & steps to reproduce

vulkan-shaders-gen is installed into /usr/ports/misc/llama-cpp/work/.build/bin/vulkan-shaders-gen imstead of /usr/local/bin/vulkan-shaders-gen

### First Bad Commit

_No response_

### Compile command

```shell
n/a
```

### Relevant log output

```shell
n/a
```