Para o comando fluttet doctor funcionasse, foi preciso adicionar a variável de ambiente.
E:\alura\flutter\src\flutter>flutter doctor
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║ Welcome to Flutter! - https://flutter.dev ║
║ ║
║ The Flutter tool uses Google Analytics to anonymously report feature usage ║
║ statistics and basic crash reports. This data is used to help improve ║
║ Flutter tools over time. ║
║ ║
║ Flutter tool analytics are not sent on the very first run. To disable ║
║ reporting, type 'flutter config --no-analytics'. To display the current ║
║ setting, type 'flutter config'. If you opt out of analytics, an opt-out ║
║ event will be sent, and then no further information will be sent by the ║
║ Flutter tool. ║
║ ║
║ By downloading the Flutter SDK, you agree to the Google Terms of Service. ║
║ Note: The Google Privacy Policy describes how data is handled in this ║
║ service. ║
║ ║
║ Moreover, Flutter includes the Dart SDK, which may send usage metrics and ║
║ crash reports to Google. ║
║ ║
║ Read about data we send with crash reports: ║
║ https://github.com/flutter/flutter/wiki/Flutter-CLI-crash-reporting ║
║ ║
║ See Google's privacy policy: ║
║ https://www.google.com/intl/en/policies/privacy/ ║
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Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.12.13+hotfix.9, on Microsoft Windows [versão 10.0.18362.418], locale pt-BR)
[X] Android toolchain - develop for Android devices
X Unable to locate Android SDK.
Install Android Studio from: https://developer.android.com/studio/index.html
On first launch it will assist you in installing the Android SDK components.
(or visit https://flutter.dev/setup/#android-setup for detailed instructions).
If the Android SDK has been installed to a custom location, set ANDROID_HOME to that location.
You may also want to add it to your PATH environment variable.
[!] Android Studio (not installed)
[!] Connected device
! No devices available
! Doctor found issues in 3 categories.