Right now when somebody wants to build Graal, in particular Substrate VM, using OpenJDK HEAD the mx tool refuses to do so early on with:

$ mx native-image
Building GraalVM with native-image in /disk/graal/upstream-sources/graal/sdk/mxbuild/linux-amd64/GRAALVM_LIBGRAAL_JAVA14_BNATIVE-IMAGE_BNATIVE-IMAGE-CONFIGURE_LLP_NI_NIC_NIL_NJU_SJVMCICOMPILER_SNATIVE-IMAGE-AGENT/graalvm-libgraal-java14-20.0.0-dev
build: Checking SubstrateVM requirements for building ...
Could not find any unresolved JVM_* symbols in static JDK libraries

Yet, there are build targets to produce statically linked versions of native libraries in OpenJDK (JDK-8232748). What's missing is to merge a JDK image with the static-libs-image libs. The result would be suitable as a build JDK for Substrate VM.