Reland with a link fix for Clang on Windows

In order to implement the --use-gl=angle Chrome flag on Linux, we need
to have the ANGLE .so directly in the build directory however GYP
places shared_libraries under lib/ on Linux. On the contrary loadable_modules
cannot be linked against so we need to keep the shared_library targets.

This commit adds _ANGLE versions of the libEGL and libGLESv2 targets as
loadable module that depend on their respective shared library.

BUG=522967

Change-Id: Iad968ab786b94b6041c279921de99633d23b48a7
Reviewed-on: https://chromium-review.googlesource.com/318470
Tryjob-Request: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>