Auto merge of #8054 - jclulow:unix-progress, r=alexcrichton

enable progress bar on all UNIX platforms

The progress bar rendered at the base of ongoing output from Cargo is presently only drawn on a subset of UNIX platforms: FreeBSD, Linux, and Mac OS.  The functionality required is basic, and essentially universally available: `ioctl()`, `TIOCGWINSZ`, and `STDERR_FILENO`.

When your platform is not in this list, the difference in behaviour is subtle and the exact mechanism is difficult to locate.  It would be better to fail to build on new ports until these definitions become available in the libc crate for those platforms.

src/cargo/core/shell.rs

@@ -379,7 +379,7 @@ impl ColorChoice {
     }
 }
 
-#[cfg(any(target_os = "linux", target_os = "macos", target_os = "freebsd"))]
+#[cfg(unix)]
 mod imp {
     use super::Shell;
     use std::mem;
@@ -408,18 +408,6 @@ mod imp {
     }
 }
 
-#[cfg(all(
-    unix,
-    not(any(target_os = "linux", target_os = "macos", target_os = "freebsd"))
-))]
-mod imp {
-    pub(super) use super::default_err_erase_line as err_erase_line;
-
-    pub fn stderr_width() -> Option<usize> {
-        None
-    }
-}
-
 #[cfg(windows)]
 mod imp {
     use std::{cmp, mem, ptr};
@@ -476,13 +464,7 @@ mod imp {
     }
 }
 
-#[cfg(any(
-    all(
-        unix,
-        not(any(target_os = "linux", target_os = "macos", target_os = "freebsd"))
-    ),
-    windows,
-))]
+#[cfg(windows)]
 fn default_err_erase_line(shell: &mut Shell) {
     if let Some(max_width) = imp::stderr_width() {
         let blank = " ".repeat(max_width);