Support the SearchType argument for loading libraries with posix. When a local shared library should be loaded, resolve its full path before calling dlopen. This logic matches SwiftShader's library loading. This is a speculative fix for Chrome being unable to load ANGLE libraries when they are distributed as part of a Chromium.app and have a different path than the executable. BUG=982294 Change-Id: Ib70096eac7460417ea7ea32941e2273dd368e6ac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1724910 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Clemen Deng <clemendeng@google.com>