all: remove darwin/386

[andybons]

Per #34749, we’re going to remove darwin/386 for Go 1.15. This is a tracking issue for that work.

Some affected files (taken from above issue. Thanks, @bradfitz):

./runtime/rt0_darwin_386.s
./runtime/cgo/gcc_darwin_386.c
./runtime/signal_darwin_386.go
./runtime/defs_darwin_386.go
./runtime/sys_darwin_386.s
./debug/macho/testdata/gcc-386-darwin-exec
./debug/macho/testdata/fat-gcc-386-amd64-darwin-exec
./debug/macho/testdata/clang-386-darwin.obj
./debug/macho/testdata/clang-386-darwin-exec-with-rpath
./cmd/vendor/golang.org/x/sys/unix/zsyscall_darwin_386.1_11.go
./cmd/vendor/golang.org/x/sys/unix/asm_darwin_386.s
./cmd/vendor/golang.org/x/sys/unix/zerrors_darwin_386.go
./cmd/vendor/golang.org/x/sys/unix/syscall_darwin_386.go
./cmd/vendor/golang.org/x/sys/unix/zsyscall_darwin_386.s
./cmd/vendor/golang.org/x/sys/unix/zsysnum_darwin_386.go
./cmd/vendor/golang.org/x/sys/unix/zsyscall_darwin_386.go
./cmd/vendor/golang.org/x/sys/unix/ztypes_darwin_386.go
./syscall/asm_darwin_386.s
./syscall/zerrors_darwin_386.go
./syscall/syscall_darwin_386.go
./syscall/zsyscall_darwin_386.s
./syscall/zsysnum_darwin_386.go
./syscall/zsyscall_darwin_386.go
./syscall/ztypes_darwin_386.go

But also stuff in debug/macho (see below comment), cmd/link, etc.

[ianlancetaylor]

Just a note that I don't think we should remove any 386 support from debug/macho. The debug/macho package is for analyzing Mach-O files, and we should continue to support examining Mach-O 386 files even if we can no longer generate them.

[andybons]

@ianlancetaylor sgtm. Thanks for the note.

[FiloSottile]

Can we drop the darwin/386 builders from tip? I am failing them in CL 227037 but it's not worth fixing them since we are dropping the target.

[gopherbot]

Change https://golang.org/cl/226985 mentions this issue: cmd/dist: remove darwin/386 as a valid port

[gopherbot]

Change https://golang.org/cl/227181 mentions this issue: dashboard: update misc-compile--darwin description

[dmitshur]

@FiloSottile Yes, we should stop running those builders on tip (but they should still run on 1.14 and older release branches).

The misc-compile-darwin builder get its list of exact GOOS/GOARCH pairs from go tool dist list output (see here and here). So it'll stop being tested on as soon as darwin/386 is removed from tip.

I see @bradfitz already sent CL 226985 for that. If you want, you could rebase your CL on top to test it.