The previous code was relying on {compilation_unit_builder_} to check if
a section was after or before the code section. This only works for the
first section after code section, since the compilation unit builder is
then reset. Use an additional field to track this instead.

R=clemensb@chromium.org

Bug: chromium:1051912
Change-Id: Id1dfa803ecde2cf77f206ea781c007fc61168942
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2054099
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66265}