Removed test cases that do not respect lifetime/scope constraint.
See discussion in artiq-zynq repo: M-Labs/artiq-zynq#119
Referred to the patch from @dnadlinger. 5faa30a837
In the origin implementation, the `nowrite` flag literally means not writing memory at all.
Due to the usage of flags on certain functions, it results in the same issues found in artiq-zynq after optimization passes. (M-Labs/artiq-zynq#119)
A fix wrote by @dnadlinger can resolve this issue. (c1e46cc7c8)
The reason of the borrow stuff is explained in M-Labs/artiq-zynq#76 (artiq-zyna repo).
As for `cache_get()`, compiler will perform stack allocation to pre-allocate the returned structure, and pass to cache_get alongside the `key`.
However, ksupport fails to recognize the passed memory, so it will always assume the passed memory as the key.
ld.lld has a habit of not putting the headers under any load sections.
However, the headers are needed by libunwind to handle exception raised by the kernel.
Creating PT_LOAD section with FILEHDR and PHDRS solves this issue. Other PHDRS are also specified as linkers (not limited to ld.lld) will not create additional unspecified headers even when necessary.
Previously we kept GNU Binutils because they are less of a pain to support
on Windoze - the source of so many problems - but with RISC-V we need to
update LLVM anyway.
