This was necessary because we used to cross-compile the library but
compile the precomputation programs for the build host. Now it's no
longer necessary and we can cleanly link even the external ASM
(which was the intent of #935).
On the way, remove an obsolete "-I" parameter.
This header contains a static array that replaces the ecmult_context pre_g and pre_g_128 tables.
The gen_ecmult_static_pre_g program generates this header file.