This is a step towards removing the dependency on CEntryStub. The next
step will reuse BuildCCall to that end. BuildCCall is a member of
WasmGraphBuilder.

Bug: 
Change-Id: I35d3af31b15c04af3d1b877049fd9eccaef306b5
Reviewed-on: https://chromium-review.googlesource.com/549106
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46266}