A "--minimal" flag turns off all optimizing compilers and activates the
interpreter. The idea is that with this flag activated, only the
platform-specific stubs and a Turbofan implementation must be complete to start
d8 and run the bulk of the tests. Note that although this flag is constructed as
a runtime flag, it must be set to true when building the snapshot and therefore
creates a compile-time dependency.

BUG=chromium:608675

Review-Url: https://codereview.chromium.org/2189663002
Cr-Commit-Position: refs/heads/master@{#38150}