Windows MASM becomes extremely slow when given very large data streams.
Runtime behavior is super-linear, with compile times of

  5s for 50 KLOC in embedded.S
 15s for 100KLOC
 40s for 150KLOC

Compilation of the 320KLOC file produced for debug builds took more than
5 minutes.

This CL reduces compile time by emitting QWORD directives instead,
which reduces the emitted debug embedded.S to around 120KLOC and
compile times to around 40s.

Bug: v8:8475,v8:6666
Change-Id: I19903cdf7d1b70a65c00ca67f40129847b17f386
Reviewed-on: https://chromium-review.googlesource.com/c/1341951Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57609}