gperf: Add a patch to work around reproducibility issues

Add a patch to avoid writing the full pathname to gperf into source
files which leads to reproducibility issues.

This fixes issues with systemd reproducibility in particular.

(From OE-Core rev: 21f36f1df42829eec0ea7b5441513d31dece960c)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit dea3c7ee2a413f7dc5f13ec006592084f7fb266c)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/gperf/gperf/reproducibility.patch

@@ -0,0 +1,26 @@
+By default gperf puts a header into generated files with the full path to
+the tool along with the commandline used. This patch removes the path to
+the binary, allowing reproducible source files (which can be included in
+debug source packages).
+
+Upstream-Status: Pending
+Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
+
+Index: gperf-3.1/src/options.cc
+===================================================================
+--- gperf-3.1.orig/src/options.cc
++++ gperf-3.1/src/options.cc
+@@ -280,6 +280,13 @@ Options::print_options () const
+     {
+       const char *arg = _argument_vector[i];
+ 
++      if (i == 0) {
++          const char *shortarg = strrchr(arg, '/');
++          if (shortarg) {
++              arg = shortarg + 1;
++          }
++      }
++
+       /* Escape arg if it contains shell metacharacters.  */
+       if (*arg == '-')
+         {

meta/recipes-extended/gperf/gperf_3.1.bb

@@ -9,6 +9,8 @@ SRC_URI  = "${GNU_MIRROR}/${BPN}/${BP}.tar.gz"
 SRC_URI[md5sum] = "9e251c0a618ad0824b51117d5d9db87e"
 SRC_URI[sha256sum] = "588546b945bba4b70b6a3a616e80b4ab466e3f33024a352fc2198112cdbb3ae2"
 
+SRC_URI:append = " file://reproducibility.patch"
+
 inherit autotools
 
 # The nested configures don't find the parent aclocal.m4 out of the box, so tell