Merge #1054

1054: riscv fixes r=lulf a=swolix

With these changes I can run embassy on our RISC-V processor, please consider merging this, feedback is very welcome.

I don't fully understand the code in the executor, but I have implemented a critical section by globally disabling interrupts, which means the wfi inside the critical section will hang the whole thing.

Co-authored-by: Sijmen Woutersen <sijmen.woutersen@gmail.com>

embassy-executor/Cargo.toml

@@ -31,6 +31,7 @@ flavors = [
 default = []
 std = ["embassy-macros/std", "critical-section/std"]
 wasm = ["dep:wasm-bindgen", "dep:js-sys", "embassy-macros/wasm"]
+riscv = ["embassy-macros/riscv"]
 
 # Enable nightly-only features
 nightly = []