nasmlib.h: slightly tidy up the definition of nasm_build_assert()
nasmlib.h: slightly tidy up the definition of nasm_build_assert()

"Assertion failed" is likely to be redundant with static_assert().

__attribute__((error)) is only guaranteed to work while optimizing, so
do not use it unless __OPTIMIZE__ is defined.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm