When building the vulkan library (libvk_swiftshader.so) for Fuchsia,
do not place the stripped binary to $OUT_DIR/swiftshader/ instead of
its default location (i.e. $OUT_DIR/lib/).

That's because the Fuchsia packaging scripts rely on the location
of the unstripped library ($OUT+DIR/lib.unstripped/) to find the
release one (i.e. by replacing 'lib.unstripped' with 'lib').

This resulted in a build error (see bug for details). This CL
works around the issue rather than fixing the scripts.

Bug chromium:1000668

Change-Id: I4137c9edbdc04b3b35a8a43e3f37b9e64fe5b1d7
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35968Tested-by: David Turner <digit@google.com>
Kokoro-Presubmit: David Turner <digit@google.com>
Presubmit-Ready: David Turner <digit@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>