fix: Build plugins when path to project has space

[rosen-vladimirov]

In case the path to project has space in the name and there's Android plugin that should be build, the build operation fails. The reason is usage of exec - change it to spawn, which handles the spaces correctly.

feat: Add buildAndroidPlugin hook, which is executed just before spawning the gradle build for specific plugin. The hook can be used to modify plugin's structure before building the plugin.

PR Checklist

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What is the current behavior?

Building of the plugin fails in case there's a space in the path to app.

What is the new behavior?

Plugins can be successfully build.

Fixes #3560

[Mitko-Kerezov]

Looks okay to me