Support for Gradle 5

[mb64]

Currently, android-glue requires gradle 4 to build. (It might work with Gradle 3 as well – I haven't tried it.)

The change to make it work with Gradle 5 would be to bump the gradle plugin version number. However, this also makes it potentially incompatible with older versions of Gradle. There's a chart here that relates plugin versions to required Gradle versions. (It's unfortunately missing the maximum working version of Gradle for the newer plugins.)

For reference of what versions of Gradle are in the wild, and whether they currently work with android-glue:

• Debian Jessie (LTS) has 1.5 (too old)
• Debian Stretch (stable) has 3.2.1 (too old)
• Fedora 30 (current version) has 4.4.1 (works)
• Debian Buster (testing) has 4.4.1 (works)
• Arch Linux has 5.4.1 (too new) but it's possible to compile and install 4.10.3 (works) from the AUR
• MacPorts has 5.4.1 (too new)
• Homebrew has 5.4.1 (too new)

Some alternative ways to add support for Gradle 5 are:

• Autodetect Gradle version and figure out the plugin version based on it
• Add a manifest key for the Gradle version and figure out the plugin version based on it
• Add a manifest key for the plugin version

[mb64]

Closing because #223 removed Gradle.