This reverts commit 2a93a26d91, which a change to use `defined` so that the GN script does not crash in
Flutter.
Fixesflutter/devtools#9786
See go/moving-devtools-to-dart-sdk-2025.
In this change, we make the source of devtools be configurable, in
actions like build_sdk.
If `build_devtools_from_sources` is true, we build local devtools,
and if false, we continue to use the prebuilt sources.
This may be an intermediate step, while we test out building devtools
from source. Or it may be permanently be a choice, if we keep building
with CIPD.
Change-Id: I9d509b07971942f2c4884224a6efda9001522bd4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/502120
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Sam Rawlins
3de2ddee09