bug#68545: warnings from GNU Make 3.81

[Mattias Engdegård]

Building with GNU Make 3.81, which seems to be supported, gives the warnings

/Applications/Xcode.app/Contents/Developer/usr/bin/make -C java bootstrap-clean
Makefile:157: warning: overriding commands for target `&'
Makefile:151: warning: ignoring old commands for target `&'
Makefile:168: warning: overriding commands for target `&'
Makefile:157: warning: ignoring old commands for target `&'
Makefile:296: warning: overriding commands for target `&'
Makefile:168: warning: ignoring old commands for target `&'

That version probably doesn't like '&'. Given that I'm not building anything in 
the java/ directory anyway, perhaps  that sub-make can be avoided altogether 
for platforms other than Android?