Build EC as a submodule, specifying version

For models that use System76 EC, we want to have the board version and
the EC version matich.

Ref: https://github.com/system76/firmware-open/issues/75

.gitmodules

@@ -94,3 +94,7 @@
 	path = tools/ipxe
 	url = https://github.com/ipxe/ipxe.git
 	branch = master
+[submodule "ec"]
+	path = ec
+	url = https://github.com/system76/ec.git
+	branch = master

models/darp5/ec.config

@@ -0,0 +1 @@
+BOARD=system76/darp5

models/darp6/ec.config

@@ -0,0 +1 @@
+BOARD=system76/darp5

models/galp3-c/ec.config

@@ -0,0 +1 @@
+BOARD=system76/galp3-c

models/galp4/ec.config

@@ -0,0 +1 @@
+BOARD=system76/galp3-c

models/lemp9/ec.config

@@ -0,0 +1 @@
+BOARD=system76/lemp9

scripts/_build/ec.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+set -e
+
+if [ -z "$1" -o ! -e "$1" -o -z "$2" ]
+then
+    echo "$0 <config> <output>" >&2
+    exit 1
+fi
+
+source "$1"
+make -C ec clean
+make -C ec BOARD=${BOARD} VERSION=${VERSION} -j $(nproc)
+cp "ec/build/${BOARD}/${VERSION}/ec.rom" "$2"

scripts/build.sh

@@ -4,7 +4,7 @@ set -e
 
 if [ -z "$1" ]
 then
-  echo "$0 [model]" >&2
+  echo "$0 <model>" >&2
   exit 1
 fi
 MODEL="$1"
@@ -79,6 +79,15 @@ KERNELVERSION="${VERSION}" \
         "${MODEL_DIR}/coreboot.config" \
         "${COREBOOT}"
 
+# Rebuild EC firmware for System76 EC models
+if [ ! -e  "${MODEL_DIR}/ec.rom" -a -e "${MODEL_DIR}/ec.config" ]
+then
+    env VERSION="${VERSION}" \
+        ./scripts/_build/ec.sh \
+        "${MODEL_DIR}/ec.config" \
+        "${BUILD}/ec.rom"
+fi
+
 if [ "${MODEL}" != "qemu" ]
 then
     # Rebuild firmware-update