cmd/flux-version: show libflux-security version

If flux-core is compiled --with-flux-security, include
the output of flux_security_version_string() in the
flux-version output.

Make this conditional on the definition of the cpp symbol
FLUX_SECURITY_VERSION_STRING, so that in the short term,
flux-core works with older versions of flux-security that
don't define flux_security_version_string().

src/cmd/builtin/version.c

@@ -25,6 +25,9 @@
 #include <config.h>
 
 #include "builtin.h"
+#if HAVE_FLUX_SECURITY
+#include <flux/security/version.h>
+#endif
 
 
 static void print_broker_version (optparse_t *p)
@@ -39,14 +42,17 @@ static void print_broker_version (optparse_t *p)
         log_err_exit ("flux_open %s failed", uri);
     if (!(version = flux_attr_get (h, "version", NULL)))
         log_err_exit ("flux_attr_get");
-    printf ("broker:  \t%s\n", version);
-    printf ("FLUX_URI:\t%s\n", uri);
+    printf ("broker:  \t\t%s\n", version);
+    printf ("FLUX_URI:\t\t%s\n", uri);
 }
 
 static int cmd_version (optparse_t *p, int ac, char *av[])
 {
-    printf ("commands:    \t%s\n", FLUX_CORE_VERSION_STRING);
-    printf ("libflux-core:\t%s\n", flux_core_version_string ());
+    printf ("commands:    \t\t%s\n", FLUX_CORE_VERSION_STRING);
+    printf ("libflux-core:\t\t%s\n", flux_core_version_string ());
+#ifdef FLUX_SECURITY_VERSION_STRING
+    printf ("libflux-security:\t%s\n", flux_security_version_string ());
+#endif
     print_broker_version (p);
 
     return (0);