[TESTBUG] Fix JTReg javac test failures with Graal

JTReg javac tests:
  langtools/tools/javac/modules/InheritRuntimeEnvironmentTest.java
  langtools/tools/javac/file/LimitedImage.java
failed when Graal is used as JVMCI compiler.

Error message shows Graal not found in these tests
Exception during HotSpotJVMCIRuntime initialization:
jdk.vm.ci.common.JVMCIError: JVMCI compiler 'graal' not found
at jdk.vm.ci.hotspot.HotSpotJVMCICompilerConfig.getCompilerFactory(jdk.internal.vm.ci@14-internal/HotSpotJVMCICompilerConfig.java:99)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.<init>(jdk.internal.vm.ci@14-internal/HotSpotJVMCIRuntime.java:466)
at jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime(jdk.internal.vm.ci@14-internal/HotSpotJVMCIRuntime.java:178)
at jdk.vm.ci.runtime.JVMCI.initializeRuntime(jdk.internal.vm.ci@14-internal/Native Method)
at jdk.vm.ci.runtime.JVMCI.getRuntime(jdk.internal.vm.ci@14-internal/JVMCI.java:65)