Revert of [build] Introduce an embedder version string (patchset #3 id:40001 of https://codereview.chromium.org/2619213002/ )

Reason for revert:
Blocks roll https://codereview.chromium.org/2647183002/

Original issue's description:
> [build] Introduce an embedder version string
>
> Sometimes, the embedder might want to merge a fix to an abandoned branch
> or to a supported branch but the fix is not relevant to Chromium.
> This adds a new version string that the embedder can set on compile time
> and that will be appended to the official V8 version.
> The separator must be provided in the string. For instance, to have a
> full version string like "5.5.372.37.custom.1", the embedder must set
> V8_EMBEDDER_STRING to ".custom.1".
>
> Related Node.js issue: https://github.com/nodejs/node/pull/9754
>
> BUG=v8:5740
> R=machenbach@chromium.org,hablich@chromium.com,ofrobots@google.com
>
> CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_rel_ng
>
> Review-Url: https://codereview.chromium.org/2619213002
> Cr-Original-Commit-Position: refs/heads/master@{#42175}
> Committed: https://chromium.googlesource.com/v8/v8/+/fc86d4329b253bf21c1dd85469f1ef4b6e5ba01a
> Review-Url: https://codereview.chromium.org/2619213002
> Cr-Commit-Position: refs/heads/master@{#42582}
> Committed: https://chromium.googlesource.com/v8/v8/+/2c1d1e60883882011ed50310a9b09e95dc61234a

TBR=hablich@chromium.com,machenbach@chromium.org,ofrobots@google.com,mic.besace@gmail.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5740

Review-Url: https://codereview.chromium.org/2643393004
Cr-Commit-Position: refs/heads/master@{#42583}