Build fails on Arch Linux and Ubuntu 17.10

[hybridNeo]

I am trying to build but the following with it fails while building qemu.

opensgx/qemu/user-exec.c:214:41: error: dereferencing pointer to incomplete type ‘struct ucontext’
 #define PC_sig(context)       ((context)->uc_mcontext.gregs[REG_RIP])

I have tried downgrading my g++ version to 6.x yet the error persists.