Error when running the emulator on Flutter in Android Studio
That alert comes up very often but the emulator starts up nevertheless. If the emulator doesn't start, click the down button(next to the play button for your emulator in the AVD manager) and select stop/disable to stop the process and try again.
I ran into this while running Cygwin on Windows with a repo I'd cloned using the Cygwin git. It looks as if Flutter launches things differently from regular Android Studio.
I was able to solve this with:
cd \users\(me)\AppData\Local\Android\Sdk\platform-toolschmod -R u+x *(That's the Cygwin /usr/bin/chmod on my path.) After that, adb started in a Flutter project.