[PATCH v2 app-xkbcomp] config: allow to build tarball when yacc is missing

[Gaetan Nadon]

Autoconf does not handle this scenario as well as Automake does.
If xkbparse.c is already there, do not abort the configuration
if yacc is missing as it is not needed.

If both xkbparse.c and yacc are missing, abort configuration.
Yacc is a required tool to build the package.

Reported-by: Julien Cristau <jcristau at debian.org>
Signed-off-by: Gaetan Nadon <memsize at videotron.ca>
---
 configure.ac |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6ed68c6..057fdbf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,7 +36,8 @@ AM_CONFIG_HEADER(config.h)
 AC_PROG_CC
 AC_PROG_YACC
 AC_PATH_PROG([YACC_INST], $YACC)
-test -z "$YACC_INST" && AC_MSG_ERROR([yacc not found - unable to compile xkbparse.y])
+AC_CHECK_FILE([$srcdir/xkbparse.c], [],
+              [test -z "$YACC_INST" && AC_MSG_ERROR([yacc not found - unable to compile xkbparse.y])])
 AC_PROG_INSTALL
 
 
-- 
1.6.0.4

Second edition. Use $srcdir for VPATH build (distcheck)