Rust timer example

[nebkor]

OK, I think this branch is reasonably ready to merge into main, provided @dbt signs off on being able to build it on his system.

[dbt]

Still failing for me, I'm guessing I'm missing a weird path dependency because I still have all the necessary compiler packages installed to build the C stuff.

% cargo clean
% git clean -fdx
% cargo build 
   Compiling libc v0.2.126
   Compiling memchr v2.5.0
   Compiling glob v0.3.0
   Compiling proc-macro2 v1.0.39
   Compiling cfg-if v1.0.0
   Compiling unicode-ident v1.0.0
   Compiling log v0.4.17
   Compiling regex-syntax v0.6.26
   Compiling minimal-lexical v0.2.1
   Compiling compiler_builtins v0.1.71
   Compiling unicode-width v0.1.9
   Compiling humantime v2.1.0
   Compiling vec_map v0.8.2
   Compiling ansi_term v0.12.1
   Compiling strsim v0.8.0
   Compiling bitflags v1.3.2
   Compiling either v1.6.1
   Compiling termcolor v1.1.3
   Compiling bindgen v0.59.2
   Compiling cc v1.0.73
   Compiling rustc-hash v1.1.0
   Compiling peeking_take_while v0.1.2
   Compiling shlex v1.1.0
   Compiling lazy_static v1.4.0
   Compiling syn v1.0.95
   Compiling core v0.0.0 (/home/dbt/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
   Compiling lazycell v1.3.0
   Compiling libloading v0.7.3
   Compiling textwrap v0.11.0
   Compiling clang-sys v1.3.2
   Compiling quote v1.0.18
   Compiling aho-corasick v0.7.18
   Compiling nom v7.1.1
   Compiling ex-timer v0.1.0 (/home/dbt/Projects/OS/os-workshop/rust/ex-timer)
   Compiling atty v0.2.14
   Compiling which v4.2.5
   Compiling clap v2.34.0
   Compiling regex v1.5.6
   Compiling env_logger v0.9.0
   Compiling cexpr v0.6.0
   Compiling tiny-rt-macros v0.1.0 (/home/dbt/Projects/OS/os-workshop/rust/tiny-rt-macros)
   Compiling tiny-rt v0.1.0 (/home/dbt/Projects/OS/os-workshop/rust/tiny-rt)
   Compiling rustc-std-workspace-core v1.99.0 (/home/dbt/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
   Compiling cty v0.2.2
error: failed to run custom build command for `tiny-rt v0.1.0 (/home/dbt/Projects/OS/os-workshop/rust/tiny-rt)`

Caused by:
  process didn't exit successfully: `/home/dbt/Projects/OS/os-workshop/rust/target/debug/build/tiny-rt-d299a17e28995c0f/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-changed=../../external/vgafonts.c
  cargo:rerun-if-changed=platform_bindings.h
  cargo:rerun-if-changed=build.rs
  cargo:rustc-link-arg=-Tmake/app.ram.ld
  cargo:rustc-link-arg=-melf32lriscv
  cargo:rustc-link-search=/home/dbt/Projects/OS/os-workshop/rust/target/riscv32ima-unknown-none-elf/debug/build/tiny-rt-7eb4ad6a0c5dd89c/out

  --- stderr
  ./../../hw/inc/hw/platform.h:43:10: fatal error: 'stdint.h' file not found
  ./../../hw/inc/hw/platform.h:43:10: fatal error: 'stdint.h' file not found, err: true
  thread 'main' panicked at 'Could not generate Rust bindings from platform_bindings.h: ()', tiny-rt/build.rs:38:10
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
% 

[nebkor]

Well, telling bindgen to pretend to be an assembler didn't break anything, so if you can verify that works for you, call it good?