[patch] find libgcj.so when version of gcc != version of gcj

[Florian Weimer]

* Matthias Klose:

> -+JAVALIB         = -L$(BOOTDIR)/jre/lib/$(LIBARCH) -lgcj $(JVMLIB)
> ++JAVALIB         = -L$(BOOTDIR)/jre/lib/$(LIBARCH) -L$(dir $(shell $(if $(GCJ),$(GCJ),$(subst gcc,gcj,$(CC))) --print-file-name=libgcj.so)) -lgcj $(JVMLIB)

Maybe use :=, to prevent repeated expansion?  (But I'm not really good
at this make stuff.)