shared-libuv is ignored by uvwasi.gyp

* **Version**: all versions since deps/uvwasi
* **Platform**: all i guess
* **Subsystem**: config/build

### What steps will reproduce the bug?

./configure --shared-libuv

### What is the expected behavior?

Do not build deps/uv, use system shared library.

### What do you see instead?

uv.gyp is pulled by uvwasi and deps/uv is built
