Added support kernel incremental build

Signed-off-by: yijian <salient.yijian@huawei.com>

BUILD.gn

@@ -36,10 +36,22 @@ if (defined(ohos_lite)) {
   kernel_build_script_dir = "//kernel/linux/build"
   kernel_source_dir = "//kernel/linux/$linux_kernel_version"
 
+  action("check_build") {
+    script = "check_build.sh"
+    sources = [ kernel_source_dir ]
+    outputs = [ "$root_build_dir/kernel.timestamp" ]
+    args = [
+      rebase_path(kernel_source_dir, root_build_dir),
+      rebase_path("$root_build_dir/packages/phone/images/uImage"),
+      rebase_path("$root_build_dir/kernel.timestamp"),
+    ]
+  }
+
   action("build_kernel") {
     script = "build_kernel.sh"
     sources = [ kernel_source_dir ]
 
+    deps = [ ":check_build" ]
     product_path = "vendor/$product_company/$product_name"
     build_type = "standard"
     outputs = [ "$root_build_dir/packages/phone/images/uImage" ]

build_kernel.sh

@@ -19,10 +19,11 @@ set -e
 #$2 - kernel build script stage dir
 #$3 - GN target output dir
 
-
+echo build_kernel
 pushd ${1}
 ./kernel_module_build.sh ${2} ${4} ${5} ${6} ${7} ${8}
 mkdir -p ${3}
+rm -rf ${3}/../../../kernel.timestamp
 cp ${2}/kernel/OBJ/${8}/arch/arm/boot/uImage ${3}/uImage
 cp ${2}/kernel/OBJ/${8}/arch/arm/boot/zImage-dtb ${3}/zImage-dtb
 popd

check_build.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+# Copyright (c) 2021 Huawei Device Co., Ltd.
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+set -e
+
+function readfile ()
+{
+    for file in $1/*
+    do
+        if [ -d $file ];then
+	    readfile $file $2 $3
+        elif [ $file -nt $2 ]; then
+            echo $file is update
+            touch $3;
+            return
+        fi
+    done
+}    
+
+echo $1 for check kernel dir
+echo $2 for output image
+echo $3 for timestamp
+if [ -e $2 ]; then
+    readfile $1 $2 $3
+    if [ $3 -nt $2 ]; then
+        echo "need update $2"
+        rm -rf $2;
+    fi
+fi
+