Target 24 seems to require JDK 1.8 as default
See https://gitlab.com/dschuermann/fdroidclient/builds/1904395.
- Can previous target versions build fine with JDK 1.8? They probably can, but should they?
- If not, how can we have this
JAVA_HOMEduality between 1.7 and 1.8?
Note that we already have both in the buildserver for retrolambda, but 1.7 is the default.
This is important because any apps targeting 24 or later will hit this.