unwind: bump `unwinding` dependency to 0.2.6
Xous now fails to compile under nightly, due to the recent change where `#[naked]` must now be wrapped in `unsafe(...)`. The `unwinding` crate was updated to account for this.
With the following `bootstrap.toml`:
```
profile = "library"
change-id = 138934
[build]
build-stage = 2
target = ["riscv32imac-unknown-xous-elf"]
[rust]
std-features = ["panic-unwind"]
download-rustc = false
```
The build fails when trying unwinding v0.2.5:
```
$ ./x.py build
[...]
Compiling unwinding v0.2.5
error: unsafe attribute used without unsafe
--> /home/user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/unwinding-0.2.5/src/unwinder/arch/riscv32.rs:176:3
|
176 | #[naked]
| ^^^^^ usage of unsafe attribute
|
help: wrap the attribute in `unsafe(...)`
|
176 | #[unsafe(naked)]
| +++++++ +
error: could not compile `unwinding` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
Build completed unsuccessfully in 0:06:26
$
```
This patch updates `unwinding` to v0.2.6, which now wraps all issues of `naked` in `unsafe()`.
1d642e5e4a