The -fdump-go-spec flag to GCC recently changed to be more fastidious about handling incomplete types. This caused some breakage in mk[r]sysinfo.sh on Solaris. This commit adjusts for the new behavior. Specifically: * Types that refer to _in6_addr may be hidden behind a typedef and can no longer be filtered out with `grep -v in6_addr`. Instead just rewrite the definition of _in6_addr to [16]byte wherever it appears. * timestruc_t is now (correctly) emitted as an alias for timespec, so this case is handled specially. * stdio.h is included in sysinfo.c to avoid emitting an incomplete definition of the FILE type. * Dummy definitions for _u?pad128_t are now emitted automatically, which conflict with the definitions installed by mk[r]sysinfo.sh. These definitions were actually dead code, so just remove them. Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/278672