[jvm] Cannot import class that imports non-existant class

[LordMZTE]

When specifying an external java library using --java-lib, Haxe will fail to compile the Haxe source if it references a class from the external library that imports another class which isn't found in the compile-time classpath.

This is valid on the Java side, as a library that optionally depends on another might have imports for classes of that library. This only results in a runtime error if the imported class is used at runtime (meaning, that references merely existing is unproblematic), thus such Haxe code should compile.