Fix out-of-source build (VPATH build).

This is achieved by inserting the $(srcdir) variable into the -I compiler option.
---
 toolkit/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/toolkit/Makefile.am b/toolkit/Makefile.am
index 4c069fb..174bade 100644
--- a/toolkit/Makefile.am
+++ b/toolkit/Makefile.am
@@ -1,4 +1,4 @@
-AM_CPPFLAGS = -I$(includedir) -I../src @LIBGCRYPT_CFLAGS@
+AM_CPPFLAGS = -I$(includedir) -I$(srcdir)/../src @LIBGCRYPT_CFLAGS@
 
 noinst_HEADERS = aes.h ctrmode.h parse.h sesskeys.h readotr.h sha1hmac.h
 
--