Building with Clang

[mtg]

It appears that iPXE can't be built with Clang. I tried and ran into issues, particularly:

core/settings.c:310:8: error: fields must have a constant size: 'variable length array in structure' extension will never be supported
char name[ strlen ( name ) + 1 /* NUL */ ];


This is after making with NO_WERROR=1 to get around several clang warning as well. This is with clang version 4.0.1-10.