ExitStatus stop signal display test: Make it Linux only

MacOS uses a different representation.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

Author: ijackson

library/std/src/sys/unix/process/process_unix/tests.rs

@@ -11,8 +11,13 @@ fn exitstatus_display_tests() {
     t(0x0008b, "signal: 11 (core dumped)");
     t(0x00000, "exit code: 0");
     t(0x0ff00, "exit code: 255");
-    t(0x0137f, "stopped (not terminated) by signal: 19");
-    t(0x0ffff, "continued (WIFCONTINUED)");
+
+    // On MacOS, 0x0137f is WIFCONTINUED, not WIFSTOPPED.  Probably *BSD is similar.
+    //   https://github.com/rust-lang/rust/pull/82749#issuecomment-790525956
+    // The purpose of this test is to test our string formatting, not our understanding of the wait
+    // status magic numbers.  So restrict these to Linux.
+    #[cfg(target_os = "linux")] t(0x0137f, "stopped (not terminated) by signal: 19");
+    #[cfg(target_os = "linux")] t(0x0ffff, "continued (WIFCONTINUED)");
 
     // Testing "unrecognised wait status" is hard because the wait.h macros typically
     // assume that the value came from wait and isn't mad.  With the glibc I have here