Add support for reproducible builds.

Suggested by Richard Purdie <richard.purdie@linuxfoundation.org> in
<https://lists.gnu.org/archive/html/bug-gperf/2022-07/msg00000.html>.

* autogen.sh: Import also lib/filename.h.
* Makefile.in (IMPORTED_FILES): Add lib/filename.h.
* src/options.cc: Include filename.h.
(Options::print_options): Print only the base name of the program name.
* tests/*.exp: Update.

src/options.cc

@@ -26,6 +26,7 @@
 #include <string.h> /* declares strcmp() */
 #include <ctype.h>  /* declares isdigit() */
 #include <limits.h> /* defines CHAR_MAX */
+#include "filename.h"
 #include "getopt.h"
 #include "version.h"
 
@@ -280,6 +281,16 @@ Options::print_options () const
     {
       const char *arg = _argument_vector[i];
 
+      if (i == 0)
+        {
+          /* _argument_vector[0] is the program name.  Print only its base name.
+             This is useful for reproducible builds.  */
+          const char *p = arg + strlen (arg);
+          while (p > arg && ! ISSLASH (p[-1]))
+            p--;
+          arg = p;
+        }
+
       /* Escape arg if it contains shell metacharacters.  */
       if (*arg == '-')
         {