build: add option --enable-host-bios

Add option to enable building in support for the host bios.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I324fc071f07cd364fd39c7df1ccfd9f0fd509a46
diff --git a/bmc/phosphor-ipmi-flash-bios-update.target.in b/bmc/phosphor-ipmi-flash-bios-update.target.in
new file mode 100644
index 0000000..46759ed
--- /dev/null
+++ b/bmc/phosphor-ipmi-flash-bios-update.target.in
@@ -0,0 +1,2 @@
+[Unit]
+Description=Phosphor-ipmi-flash update the BIOS image