printer: make compilation on non-unix, non-windows platforms work

Some of the new hyperlink work caused ripgrep to stop compiling
on non-{Unix,Windows} platforms. The most popular of which is WASI.

This commit makes non-{Unix,Windows} compile again. And we add a
very basic WASI test in CI to catch regressions.

More work is needed to make tests on non-{Unix,Windows} platforms
work. And of course, this commit specifically takes the path of disabling
hyperlink support for non-{Unix,Windows} platforms.

crates/cli/src/hostname.rs

@@ -25,10 +25,10 @@ pub fn hostname() -> io::Result<OsString> {
     }
     #[cfg(not(any(windows, unix)))]
     {
-        io::Error::new(
+        Err(io::Error::new(
             io::ErrorKind::Other,
             "hostname could not be found on unsupported platform",
-        )
+        ))
     }
 }