fix(cloud_functions): ci failures

[Salakar]

Description

Fix for CI failures highlighted in #2499.

• Added missing gradle.properties AndroidX properties to cloud_functions example repository
• Updated environment SDK version range to fix Packages with an SDK constraint on a pre-release of the Dart SDK should themselves be published as a pre-release version. If this package needs Dart version 2.0.0-dev.28.0, consider publishing the package as a pre-release instead. CI publishable issue.

Before

After

Related Issues

• CI is red #2499 - "CI is red"

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Breaking Change

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• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
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[cyanglaz]

Just saw this PR. We should probably increase the dark sdk lower bound instead of decreasing it. Any particular language feature we need in the plugin in 2.0.0?

[Salakar]

Just saw this PR. We should probably increase the dark sdk lower bound instead of decreasing it. Any particular language feature we need in the plugin in 2.0.0?

Isn't changing 2.0.0-dev.28.0 to 2.0.0 increasing the lower bound SDK version already?

• 2.0.0-dev.28.0 (OLDER) was released 17th Feb 2018 - https://github.com/dart-lang/sdk/releases/tag/2.0.0-dev.28.0
• 2.0.0 (NEWER) was released 6th Aug 2018 - https://github.com/dart-lang/sdk/releases/tag/2.0.0

The change was just to remove it from referencing pre-release versions of the Dart SDK - changing to 2.0.0 was the initial safest bet I thought with the least upgrade/changes friction.