We recently changed embedded builtins to be emitted as raw assembly
files during the build process in order to support MSVC (which doesn't
support inline assembly on x64). Ninja uses ml.exe / ml64.exe as the
assembler on all Windows builds (msvc & clang); these unfortunately
don't support large data streams well and can take over 5 minutes for
embedded.S.

With this CL we work around this by going back to inlined assembly for
clang Windows builds.

Bug: v8:6666, v8:8475
Change-Id: I33beb3f5a1df07de3299df0fc2be4e8983701db0
Reviewed-on: https://chromium-review.googlesource.com/c/1344114
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Sergiy Belozorov <sergiyb@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57726}