We too have a combination of languages and also across platforms (Linux, Solaris, Windows etc) and Ant works well.
What would be the best compile tool? Ant is a build tool, for compile tool, you're stuck with the JDK's "javac" program and for C/C++ you would use Visual Studio's command line tools like msbuild.exe, vcbuild.exe (read up on their documentation on how to invoke them via command line), for Unix you'll most likely use GCC in combination with "make" and makefiles...