Test GraalVM 20 dev build

[borkdude]

See https://github.com/graalvm/graalvm-ce-dev-builds/releases

• verify if things still work with jdk8 (mac, linux and windows)

• is this fixed for jdk11? [native-image] Reflection config with java.nio.file.Files does not work with JDK 11 on macOS 10.14.6 oracle/graal#2015 (comment)

• is this fixed for windows? [native-image] LINK : fatal error LNK1181: cannot open input file 'stdc++.lib' on Windows oracle/graal#1876

• windows build (without 1784 and 1876) graalvm 20 jdk11 works, see branch windows-graalvm20-jdk11)

• is this fixed for windows? [native-image] Failed to build the native image on Windows when using Signal.handle oracle/graal#1784
  not yet: [native-image] Failed to build the native image on Windows when using Signal.handle oracle/graal#1784 (comment)

• is there a fix for dealing with javax.xml? Agent omitted one reflection: javax.xml.stream.FactoryConfigurationError: Provider com.sun.xml.internal.stream.XMLInputFactoryImpl not found oracle/graal#1387

[FieryCod]

@borkdude did you check whether graal#1387 is fixed? That's the only reason I stopped developing holy-lambda.

[borkdude]

I know as much about graal#1387 as you do :). Might be good poking the devs on the graal slack about it.