mk: Split target triples into bulid triple + host triples + target triples

For cross compiling to targets that don't want to build a compiler
mk: Refactor platform.mk a bit
submodule: libuv for android
mk: rewrite make files
mk: mingw32 flags added
mk: mingw32 fix
mk: Cross-compile fixes
Update uv submodule
mk: Restore toolchain config for i386 mac/linux, and freebsd
mk: Fix check-fast
mk: Fix cross-compile to targets other than android
mk: Fix install for cross-compilers