llvm::Optional::value => operator*/operator->

std::optional::value() has undesired exception checking semantics and is
unavailable in older Xcode (see _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS). The
call sites block std::optional migration.

This makes `ninja clang` work in the absence of llvm::Optional::value.

GitOrigin-RevId: 53e5cd4d3e39dad47312a48d4c6c71318bb2c283
1 file changed