setcap: fix errno display

The commit 056ffb0bd25d91ffbcb83c521fc4d3d9904ec4d4 broke the display of
the final error message because it would do more operations that would
clobber errno.  Example:
(libcap-2.22) sudo setcap cap_ipc_lock=ep /proc/filesystems | head -1
Failed to set capabilities on file `/proc/filesystems' (Operation not supported)
(libcap-2.23) sudo setcap cap_ipc_lock=ep /proc/filesystems | head -1
Failed to set capabilities on file `/proc/filesystems' (Invalid argument)

Save the original errno value and use that for the final display instead.

URL: https://bugs.gentoo.org/551672
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

progs/setcap.c

diff --git a/progs/setcap.c b/progs/setcap.c
index 83090ae..7304343 100644
--- a/progs/setcap.c
+++ b/progs/setcap.c
@@ -171,6 +171,7 @@
 	    retval = cap_set_file(*++argv, cap_d);
 	    if (retval != 0) {
 		int explained = 0;
+		int oerrno = errno;
 #ifdef linux
 		cap_value_t cap;
 		cap_flag_value_t per_state;
@@ -193,7 +194,7 @@
 		
 		fprintf(stderr,
 			"Failed to set capabilities on file `%s' (%s)\n",
-			argv[0], strerror(errno));
+			argv[0], strerror(oerrno));
 		if (!explained) {
 		    usage();
 		}