Cygwin: uname: add host machine tag to sysname.

If the Cygwin dll's architecture is different from the host system's
architecture, append an additional tag that indicates the host system
architecture (the Cygwin dll's architecture is already indicated in
machine).

Signed-off-by: Jeremy Drake <cygwin@jdrake.com>
(cherry picked from commit 7923059bff6c120c6fb74b63c7553ea345c0a8f3)

winsup/cygwin/uname.cc

@@ -51,13 +51,27 @@ uname_x (struct utsname *name)
   __try
     {
       char buf[NI_MAXHOST + 1] ATTRIBUTE_NONSTRING;
+      int n;
 
       memset (name, 0, sizeof (*name));
       /* sysname */
       const char* sysname = get_sysname();
-      __small_sprintf (name->sysname, "%s_%s-%u",
-		       sysname,
-		       wincap.osname (), wincap.build_number ());
+      n = __small_sprintf (name->sysname, "%s_%s-%u",
+			   sysname,
+			   wincap.osname (), wincap.build_number ());
+      if (wincap.host_machine () != wincap.cygwin_machine ())
+	{
+	  switch (wincap.host_machine ())
+	    {
+	      case IMAGE_FILE_MACHINE_ARM64:
+		n = stpcpy (name->sysname + n, "-ARM64") - name->sysname;
+		break;
+	      default:
+		n += __small_sprintf (name->sysname + n, "-%04y",
+				      (int) wincap.host_machine ());
+		break;
+	    }
+	}
       /* nodename */
       memset (buf, 0, sizeof buf);
       cygwin_gethostname (buf, sizeof buf - 1);