cgdb: fix autoreconf

autoreconf needs to be told where to find macros as the Makefile.am does
not do this.

Signed-off-by: Ross Burton <ross.burton@arm.com>

meta-oe/recipes-devtools/cgdb/cgdb_0.8.0.bb

@@ -13,6 +13,8 @@ SRC_URI = "http://cgdb.me/files/${BP}.tar.gz \
            file://0001-cgdb-Do-not-search-for-cgdb.txt-in-build-dir.patch"
 SRC_URI[sha256sum] = "0d38b524d377257b106bad6d856d8ae3304140e1ee24085343e6ddf1b65811f1"
 
+EXTRA_AUTORECONF += "-I config"
+
 CACHED_CONFIGUREVARS = "ac_cv_file__dev_ptmx=yes ac_cv_rl_version=6.2 ac_cv_file__proc_self_status=yes"
 EXTRA_OECONF = "--with-readline=${STAGING_LIBDIR} \
     --with-ncurses=${STAGING_LIBDIR}"