build : provide FRU yaml as configurable input

In preparation for the openpower-vpd-parser recipe, make it possible to
provide the FRU data YAML file as a build-configurable input.

Use writefru.yaml as default.

Change-Id: I32dba99bcb6c8dd4da259f907b0499b3192cc412
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
diff --git a/configure.ac b/configure.ac
index 2cb5d9d..aca5495 100644
--- a/configure.ac
+++ b/configure.ac
@@ -42,6 +42,10 @@
     AC_SUBST([OESDK_TESTCASE_FLAGS], [$testcase_flags])
 )
 
+AS_IF([test "x$FRU_YAML" == "x"], [FRU_YAML="writefru.yaml"])
+FRUGEN="$PYTHON $srcdir/writefru.py -i $FRU_YAML"
+AC_SUBST(FRUGEN)
+
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_FILES([Makefile test/Makefile])
 AC_OUTPUT