Which Scheme?

I need a Scheme compiler and/or interpreter that is:

- Portable to at least Windows, Linux, and Mac OS X.
- Has support for file I/O in UTF-8 encoding.
- Has support for parsing command line arguments.
- Has support for running shell commands on Unix systems and basic host platform detection (am I running on Windows/Linux/OS X)?
- Implements SRFIs for at least hash tables and regular expressions.
- If any of the above features are missing, then an easy to use foreign function interface will be necessary so I can roll my own.
- Bonus points for being light-weight, easy to compile/install and get up and running quickly, and/or more modern syntax (I'm familiar with R6RS and R7RS syntax as I've written C++ lexer/parsers for both, for custom Scheme-like DSLs).

Project idea is to write a program to generate ninja build files for C/C++/assembly projects from a custom sexpr data representation describing a given project. On Unix-like systems, I'll be replacing the functionality of autoconf, so I'll be checking for library feature availability, running the installed C++ compiler, invoking pkg-config, etc. Later, I'd like to add the ability to spit out MSVS/MSBuild and Xcode project files as alternative targets.

I'm going to give Gauche Scheme a try. It seems to have been written for utility/script creation in mind. It already has library with autoconf like syntax, and meets all of the other requirements. If it fails, I'll try something else.