When customizing the list of JVM features during the "configure" phase and intentionally removing the "serialgc" feature, for example with:

./configure --with-jvm-variants=custom --with-jvm-features=cds,compiler1,compiler2,g1gc,jfr,jni-check,jvmci,jvmti,management,services --enable-generate-classlist --disable-manpages --with-vendor-name=Experiments

The build will fail later during "make images" with errors such as:

Creating java.security.jgss.jmod
Error occurred during initialization of VM
Option -XX:+UseSerialGC not supported

Ideally the build should allow this, as "serialgc" is listed as an optional feature.

I'm told a workaround could be to build the JDK twice: run a regular build and then build it again with --with-build-jdk and specify such customisations at that stage.