luk@luk-pc:/mnt/android/cm-12$ cat build.sh
. build/envsetup.sh
export USE_CCACHE=1
export PRODUCT_PREBUILT_WEBVIEWCHROMIUM=yes

#rm -rf out/target/product/baffinlite/obj/KERNEL_OBJ/source/tools/gator/daemon

mkdir -p "out/target/product/$1/system/app/webview/lib/arm"
mkdir -p "out/target/product/$1/system/lib"

`cp -R prebuilts/chromium/$1/app/* out/target/product/$1/system/app/`
`cp -R prebuilts/chromium/$1/lib/* out/target/product/$1/system/lib/`
`cp -R prebuilts/chromium/$1/app/webview/lib/arm/libwebviewchromium.so out/target/product/$1/system/app/webview/lib/arm/libwebviewchromium.so`

time brunch "$1"

============

luk@luk-pc:/mnt/android/cm-12$ cat chromium_prebuilt.sh
#!/bin/sh

# Copyright (C) 2014 The OmniROM Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# This works, but there has to be a better way of reliably getting the root build directory...
if [ $# -eq 1 ]; then
    TOP=$1
    DEVICE=`echo $TARGET_PRODUCT | sed 's/cm_//g'`
elif [ -n "$(gettop)" ]; then
    TOP=$(gettop)
    DEVICE=$(get_build_var TARGET_DEVICE)
else
    echo "Please run envsetup.sh and lunch before running this script,"
    echo "or provide the build root directory as the first parameter."
    return 1
fi

TARGET_DIR=$OUT
PREBUILT_DIR=$TOP/prebuilts/chromium/$DEVICE

if [ -d $PREBUILT_DIR ]; then
    rm -rf $PREBUILT_DIR
fi

mkdir -p $PREBUILT_DIR
mkdir -p $PREBUILT_DIR/app
mkdir -p $PREBUILT_DIR/lib

if [ -d $TARGET_DIR ]; then
    echo "Copying files..."
    cp -r $TARGET_DIR/system/app/webview $PREBUILT_DIR/app
    cp $TARGET_DIR/system/lib/libwebviewchromium.so $PREBUILT_DIR/lib/libwebviewchromium.so
    cp $TARGET_DIR/system/lib/libwebviewchromium_plat_support.so $PREBUILT_DIR/lib/libwebviewchromium_plat_support.so
    cp $TARGET_DIR/system/lib/libwebviewchromium_loader.so $PREBUILT_DIR/lib/libwebviewchromium_loader.so
else
    echo "Please ensure that you have ran a full build prior to running this script!"
    return 1;
fi

echo "Generating Makefiles..."

HASH=$(git --git-dir=$TOP/external/chromium_org/.git --work-tree=$TOP/external/chromium_org rev-parse --verify HEAD)
echo $HASH > $PREBUILT_DIR/hash.txt

(cat << EOF) | sed s/__DEVICE__/$DEVICE/g > $PREBUILT_DIR/chromium_prebuilt.mk
# Copyright (C) 2014 The OmniROM Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

LOCAL_PATH := prebuilts/chromium/__DEVICE__/

PRODUCT_COPY_FILES += \\
    \$(LOCAL_PATH)/app/webview/webview.apk:system/app/webview/webview.apk \\
    \$(LOCAL_PATH)/lib/libwebviewchromium.so:system/lib/libwebviewchromium.so \\
    \$(LOCAL_PATH)/lib/libwebviewchromium_plat_support.so:system/lib/libwebviewchromium_plat_support.so \\
    \$(LOCAL_PATH)/lib/libwebviewchromium_loader.so:system/lib/libwebviewchromium_loader.so

\$(shell mkdir -p out/target/product/__DEVICE__/system/app/webview/lib/arm/)
\$(shell cp -r \$(LOCAL_PATH)/app/webview/lib/arm/libwebviewchromium.so out/target/product/__DEVICE__/system/app/webview/lib/arm/libwebviewchromium.so)

EOF

echo "Done!"