Made GNU xorriso ready for building out-of-source. Thanks Ross Burton.

xorriso/xorriso_makefile_am.txt

@@ -1,5 +1,5 @@
 
-# Copyright (c) 2007 - 2012 Thomas Schmitt <scdbackup@gmx.net>
+# Copyright (c) 2007 - 2019 Thomas Schmitt <scdbackup@gmx.net>
 # Provided under GPL version 2 or later.
 
 # ts A90315 : LIBBURNIA_PKGCONFDIR is defined OS specific in acinclude.m4
@@ -242,14 +242,14 @@ noinst_PROGRAMS = \
 # To compare tree /media/dvd and /original/dir :
 #   find /media/dvd -exec test/compare_file '{}' /media/dvd /original/dir ';'
 #
-test_compare_file_CPPFLAGS =
+test_compare_file_CPPFLAGS = -I $(top_builddir)/xorriso
 test_compare_file_CFLAGS =
 test_compare_file_LDADD =
 test_compare_file_SOURCES = test/compare_file.c
 
 # Specialized converter from xorriso/xorriso.texi to xorriso/xorriso.1
 #
-xorriso_make_xorriso_1_CPPFLAGS =
+xorriso_make_xorriso_1_CPPFLAGS = -I $(top_builddir)/xorriso
 xorriso_make_xorriso_1_CFLAGS =
 xorriso_make_xorriso_1_LDADD =
 xorriso_make_xorriso_1_SOURCES = xorriso/make_xorriso_1.c