Partly builds on Windows should not always need C compiler

[Ulf Zibis]

Some times ago I tried to run the make for nio/charsets via CYGWIN.
It turned out, that I was required to have Visual Studio installed, because 
$(BUILDDIR)/common/Defs.gmk always looks for the C compiler.
Can this dependency interweaved in a different way, so building of JDK parts without C sources would 
be possible without a C compiler installed?

-Ulf