概要

Environment.SetEnvironmentVariable
(
    variable: "ANDROID_HOME",
    value: AndroidExternalToolsSettings.sdkRootPath,
    target: EnvironmentVariableTarget.Process
);

var oldPath = Environment.GetEnvironmentVariable
(
    variable: "PATH",
    target: EnvironmentVariableTarget.Process
);

var newPath = $@"{oldPath}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools";

Environment.SetEnvironmentVariable
(
    variable: "PATH",
    value: newPath,
    target: EnvironmentVariableTarget.Process
);