Add support for getenv as defined by the Open Group's "System Interface &
Header" in https://pubs.opengroup.org/onlinepubs/7908799/xsh/getenv.html
getenv requires a standard way of accessing the environment,
so a pointer to the environment is added to the startup in crt1.
Consquently, this function is not usable on top of other libcs.
Added starts_with method to StringView. getenv function uses it.
Co-authored-by: Jeff Bailey <jeffbailey@google.com>
Reviewed By: sivachandra, rtenneti
Differential Revision: https://reviews.llvm.org/D119403
A small collection of utils called osutils has been added. These utils
are now used in loader tests instead of the equivalent entrypoints.
The loader can now be built and tested without depending on any entrypoint.
In a follow up change, the relevent entrypoints will be updated to use the
newly added osutils.
Reviewed By: lntue, michaelrj
Differential Revision: https://reviews.llvm.org/D115655
