llvm-project `ErrorHandling.h` was updated to remove std::string. This
added a new `report_fatal_error` overload taking a `const Twine &`,
removed the overload that took `const std::string &`, and updated
`fatal_error_handler_t` to use `const char *` rather than `const
std::string &`.
Fix uses of these functions to take into account these updates. Note
that without the `const std::string &` overload, passing a `std::string`
into `report_fatal_error` now results in an ambiguous match between the
`StringRef` and `Twine` overloads so we need to be explicit about one or
the other.
Ensure that we only have one writer to the module trace file at a time by using LLVM's `LockFileManager` utilities, similarly to `ModuleInterfaceBuilder`
Resolves rdar://76743462
Follow programming guidelines for these getters more closely and have them return a non-owning view of the underlying data instead of relying on callers to take const references to the copy that is returned here.
T *const does not prevent logically non-const accesses to the underlying data, it merely indicates that the pointer value itself is const. This modifier can be cast off by a copy, so it's not generally what you want here. Switch to const T * instead.
