holy-build: Fix symbol visibility
holy-build: Fix symbol visibility

holy-build-box adds -fvisibility=hidden to CFLAGS which causes lua_ and some luv_ symbols to not be globally exported. Now, we simply remove -fvisibility=hidden from CFLAGS before compiling.

This also removes the -g flag from CFLAGS which is something else that holy-build-box sets.

Closes #219

zhaozg/luvi,zhaozg/luvi,luvit/luvi,luvit/luvi