environ variable should be updated if user provides environment. It only update for normal processes. Bug= https://github.com/dart-lang/sdk/issues/36132 Change-Id: I2a4639ed53e7376534578a0b1b251025ffaa2278 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96147 Reviewed-by: Siva Annamalai <asiva@google.com> Commit-Queue: Zichang Guo <zichangguo@google.com>