In internal/bytealg correct a +build tag to never build indexbyte_generic.go
for the gofrontend, where we always use indexbyte_native.go.
For internal/cpu let the Makefile define CacheLineSize using goarch.sh,
rather than trying to enumerate all the possibilities in cpu_ARCH.go files.
In internal/poll call the C fcntl function rather than using SYS_FCNTL.
Change mksysinfo.sh to ensure that F_GETPIPE_SZ is always defined,
and check that in internal/poll.
Reviewed-on: https://go-review.googlesource.com/137256
From-SVN: r264572
f5ec13f15d