High memory usage on serve

Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

I noticed a high memory usage using the last version of CLI when runningng serve. It starts with a normal amount of memory allocated. And then for every change made to the project files, it seems that the previous memory allocated for the build is not freed and the memory keeps growing until I have to stop the process and start again.

Versions.

Angular CLI: 1.5.0-rc.6
Node: 7.6.0
OS: win32 x64
Angular: 5.0.0-rc.8
... animations, common, compiler, compiler-cli, core, forms
... http, platform-browser, platform-browser-dynamic, router

@angular/cdk: 2.0.0-beta.12
@angular/cli: 1.5.0-rc.6
@angular/flex-layout: 2.0.0-beta.9
@angular/material: 2.0.0-beta.12
@angular-devkit/build-optimizer: 0.0.31
@angular-devkit/core: 0.0.20
@angular-devkit/schematics: 0.0.34
@ngtools/json-schema: 1.1.0
@ngtools/webpack: 1.8.0-rc.6
@schematics/angular: 0.0.48
typescript: 2.5.3
webpack: 3.8.1

Repro steps.

I would need to try on a new generated project if it does the same thing.

The log given by the failure.

Here is 2.6G of RAM allocated for the serve process.

And 5 minutes after

Desired functionality.

Mention any other details that might be useful.