On building mruby with Rake, you may got "Too many open files" error. This is harmless. Please re-run ./minirake (or make).

This issue is reported by mruby/mruby#793.

Maybe dependencies are corrupt. type ./minirake clean. Or git clean -xdf also effective.

Building on Cygwin is not well supported, because of the way paths are treated (slash vs. backslash, /cygdrive/c/ vs. C:, etc.) However, some users successfully built under Cygwin.

The key is to set up the NDK environment like so:

export ANDROID_STANDALONE_TOOLCHAIN=\`cygpath -w /tmp/android-14-toolchain\

After this, it should build if you run make.