libstdc++ build process against musl

Hi all,

I'm using musl-libc for another project, and was looking to extend C++ support to my project. The current libstdc++ that ships with most distros (e.g., Debian/Ubuntu/Fedora) is compiled against glibc, but I saw that Alpine Linux has it built against musl-libc. Could anybody describe or point me to documentation on how Alpine builds it against musl? Thanks!