at one point, clang reportedly failed to support the asm register
constraints needed for inline syscalls. versions of clang that old
have much bigger problems that preclude using them to compile musl
libc.

mips64 requires 'struct stat' conversion due to incorrect 32-bit
fields where time_t should be in the kernel version of the structure.
syscall_arch.h already performed the correct translation for stat,
fstat, and lstat syscalls, but omitted special handling for fstatat.

patch by Mahesh Bodapati and Jaydeep Patil of Imagination
Technologies.