flash-ipmi: implement flashStartHash

Change-Id: Ia134b1faef99510bbed5eb4e36dada164c010305
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index dd05a59..12763e4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -72,6 +72,10 @@
 AS_IF([test "x$STAGING_PATH" == "x"], [STAGING_PATH="/run/initramfs/bmc-image"])
 AC_DEFINE_UNQUOTED([STAGING_PATH], ["$STAGING_PATH"], [The staging path for the flash image.])
 
+AC_ARG_VAR(HASH_PATH, [The path for the hash file.])
+AS_IF([test "x$HASH_PATH" == "x"], [HASH_PATH="/tmp/bmc.sig"])
+AC_DEFINE_UNQUOTED([HASH_PATH], ["$HASH_PATH"], [The path for the hash file.])
+
 # Create configured output
 AC_CONFIG_FILES([Makefile test/Makefile])
 AC_OUTPUT