Add eu-strip to buildtools/third_party/

The build and builtools directories are provided to standalone projects
such as angle. Move eu-strip into buildtools so that those projects'
copy of build/ can find it.

Bug: angleproject:2475
Test: build standalone angle with target_os="fuchsia"
Change-Id: I44187fa253ee0070558ab2121d6829d317e62498
5 files changed