fix VM abort when ClassLoader.defineClass is used in bootimage build

When loading a class which extends another class that contained a
field of primitive array type using defineClass in a bootimage=true
build, the VM was unable to find the primitive array class, and
makeArrayClass refused to create one since it should already have
existed.

The problem was that the bootimage=true build uses an empty
Machine::BootstrapClassMap, and resolveArrayClass expected to find the
primitive array classes there.  The fix is to check the
Machine::BootLoader map if we can't find it in
Machine::BootstrapClassMap.

src/machine.cpp

@@ -1835,7 +1835,16 @@ resolveArrayClass(Thread* t, object loader, object spec, bool throw_)
 
     return c;
   } else {
-    return makeArrayClass(t, loader, spec, throw_);
+    PROTECT(t, loader);
+    PROTECT(t, spec);
+
+    c = findLoadedClass(t, root(t, Machine::BootLoader), spec);
+
+    if (c) {
+      return c;
+    } else {
+      return makeArrayClass(t, loader, spec, throw_);
+    }
   }
 }
 

test/DefineClass.java

@@ -72,6 +72,7 @@ public class DefineClass {
 
   public abstract static class Base {
     public int foo;
+    public int[] array;
     
     public void bar() { }