Compiling Jenkins core on Java 18 fails, because the antlr-maven-plugin version core uses, 2.2 while writing this, fails to generate the grammar files due to the deprecation of the security manager

Bumping the antlr-maven-plugin to an up to date version doesn't resolve the issue, because maintained versions only support ANTLR 4, which also is the current maintained and supported version of ANTLR.
Core uses ANTLR 2, which was last released in 2007.

There are currently two files located in core/src/main/grammar/*.g which would need an update from v2 to v4 to be eligible to be used by an up to date version of the antlr-maven-plugin on compile time.