Add build scripts

dev/tools/build_release.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+cd engine/src/out/
+
+et build -c ci/android_release -j $(nproc)
+et build -c host_release -j $(nproc)
+
+rm android_release || true
+ln -sf ci/android_release android_release

dev/tools/envsetup.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+ET_P=$(pwd)/engine/src/flutter/bin/
+echo "Adding $ET_P to path"
+PATH=$PATH:$ET_P
+echo "Writing flutter root path to ~/.flutter_path"
+echo $PWD > ~/.flutter_path