Fix a warning in the linux build

[Cyberboss]

warning: getting the inner pointer of a temporary `CString`
  --> auxtools/src/version.rs:62:57
   |
62 |             let module = dlopen(CString::new(BYONDCORE).unwrap().as_ptr(), RTLD_LAZY);
   |                                 -------------------------------- ^^^^^^ this pointer will be invalid
   |                                 |
   |                                 this `CString` is deallocated at the end of the statement, bind it to a variable to extend its lifetime
   |
   = note: pointers do not have a lifetime; when calling `as_ptr` the `CString` will be deallocated at the end of the statement because nothing is referencing it as far as the type system is concerned
   = help: for more information, see https://doc.rust-lang.org/reference/destructors.html
   = note: `#[warn(temporary_cstring_as_ptr)]` on by default

warning: `auxtools` (lib) generated 1 warning

[willox]

this would not have been a problem in C++ :(