[wasi-common]: add armv7 support to wasi-common (#1269)

* Add armv7 support to wasi-common

This commit enables `target_pointer_width = 32` compatibility for
`wasi-common` (and by transitivity, any crate found inside, e.g., `yanix`).
I've also added a simplistic (bare minimum) check to our CI to ensure
that `wasi-common` cross-compiles to `armv7-unknown-gnueabihf` fine.
While here, I've done the same for `wasm32-unknown-emscripten`.

* Clean arch-specific impls + reuse libc consts

* Make SeekLoc::from_raw platform independent

* Collapse CI cc jobs into one

crates/wasi-common/yanix/src/sys/emscripten/filetime.rs

@@ -5,9 +5,6 @@ use crate::from_success_code;
 use std::fs::File;
 use std::io::Result;
 
-pub(crate) const UTIME_NOW: i32 = 1_073_741_823;
-pub(crate) const UTIME_OMIT: i32 = 1_073_741_822;
-
 /// Wrapper for `utimensat` syscall. In Emscripten, there is no point in dynamically resolving
 /// if `utimensat` is available as it always was and will be.
 pub fn utimensat(

crates/wasi-common/yanix/src/sys/emscripten/mod.rs

@@ -5,21 +5,3 @@ pub(crate) mod fadvise;
 #[path = "../linux/file.rs"]
 pub(crate) mod file;
 pub(crate) mod filetime;
-
-use crate::dir::SeekLoc;
-use std::convert::TryInto;
-use std::io::{Error, Result};
-
-impl SeekLoc {
-    pub unsafe fn from_raw(loc: i64) -> Result<Self> {
-        // The cookie (or `loc`) is an opaque value, and applications aren't supposed to do
-        // arithmetic on them or pick their own values or have any awareness of the numeric
-        // range of the values. They're just supposed to pass back in the values that we
-        // give them. And any value we give them will be convertable back to `long`,
-        // because that's the type the OS gives them to us in. So return an `EINVAL`.
-        let loc = loc
-            .try_into()
-            .map_err(|_| Error::from_raw_os_error(libc::EINVAL))?;
-        Ok(Self(loc))
-    }
-}