Package map entries can contain relative paths, and these paths will be based
on the package map path as originally specified

Instead of trying to execute the script directly, use /bin/sh to execute the
script.

Switch sdk_xcode_harness to use flutter build aot

This patch moves a bunch of complexity out of FlutterApplication.xcodeproj and
into `flutter build aot`, which will make it easier for developers to create
their own FlutterApplication.xcodeproj.

This enables the specification of a local engine (via `--local-engine`)
for flutter tools to use.

* Create an Xcode project template for dynamic service creation.

The `create_native_service_sdk.py` will be run on the buildbot similar
to `create_ios_sdk.py`. This will create an Xcode project with both arm
and x64 assets that the user can use to fill in the service
implementation.

* Add the complete_static_lib property to sdk_lib_archive in
dynamic/BUILD.gn

It crashes. We either need to make it safe to call before
Dart_Initialize on Mac or we need to use some other way of measuring
startup time.

Fixes #4006

Update the flutter_gdb script to run on MacOS and make the engine build directory configurable (#2694)

Instead of depending on a potentially missing Interpreter.xcconfig, add the variable to Flutter.xcconfig. (#2689)

We still need this for the observatory build.

This reverts commit 5082974b.

The engine.git repo doesn't need a copy of the Dart SDK anymore.

Fixes https://github.com/flutter/flutter/issues/2618

When developing the engine from Xcode, it is useful to see log output in Xcode's UI. We were redirecting streams away so that the tools could pick read these logs. With the change to the scheme, when running from Xcode, the logs will show up in Xcode's UI. When, running from the tools, that flag will not be present and the tools will work as they always have.

* Added instrumentation for timings.

* A few more traces for better granularity.

Can happen when calling getWordBoundary on an empty Paragraph.

* Expose a Paragraph.getWordBoundary method to dart.

Used by text selection to select a word.

Earlier, the dynamic service loader was part of the main application
bundle. But now, we package it into Flutter.framework and let the user
control "main". The old path was looking for the manifest in the wrong
spot.

* Updating CONTRIBUTING.md to mention latest paths

* Update CONTRIBUTING.md

create_ios_sdk.py takes additional arguments that specify the out directories of both the device and simulator builds. (#2673)