Failures on [VM/dartdev] Switch dartdev to use an AOT runtime.

[a-siva]

The tests

co19/Language/Libraries_and_Scripts/Scripts/top_level_main_t01
co19/Language/Libraries_and_Scripts/Scripts/top_level_main_t06

are failing on configurations

vm-aot-linux-debug-x64
vm-aot-linux-release-x64

The failure is because the dart VM executable is renamed to dartvm in this CL and the test assumes the presence of dart in a runtime build.

[a-siva]

This has been fixed and failure is not seen in the recent tests on the CL that switches dartdev to use an AOT runtime.