build: linux-amd64-noopt builder broken

[bradfitz]

After https://go-review.googlesource.com/136855 the noopt builder is now broken with:

https://build.golang.org/log/9da226d6f602b11ab5a19b4fd54768d7ec8abc28

##### ../test
# go run run.go -- fixedbugs/issue7921.go

issue7921.go:21: missing error "inlining call"
issue7921.go:21: missing error "string\\(bytes\\.b\\.buf\\[bytes.b.off:\\]\\) escapes to heap"
issue7921.go:25: no match for `inlining call` in:
	issue7921.go:25: make([]byte, 0, 64) escapes to heap
issue7921.go:25: no match for `make\(\[\]byte, 0, 64\) does not escape` in:
	issue7921.go:25: make([]byte, 0, 64) escapes to heap
issue7921.go:25: no match for `&bytes.Buffer literal does not escape` in:
	issue7921.go:25: make([]byte, 0, 64) escapes to heap
issue7921.go:29: missing error "inlining call"
issue7921.go:33: no match for `inlining call` in:
	issue7921.go:33: make([]byte, 0, 64) escapes to heap
issue7921.go:33: no match for `make\(\[\]byte, 0, 64\) does not escape` in:
	issue7921.go:33: make([]byte, 0, 64) escapes to heap
issue7921.go:33: no match for `&bytes.Buffer literal does not escape` in:
	issue7921.go:33: make([]byte, 0, 64) escapes to heap
issue7921.go:38: missing error "inlining call"
issue7921.go:38: missing error "string\\(bytes.b.buf\\[bytes\\.b\\.off:\\]\\) escapes to heap"
issue7921.go:45: no match for `inlining call` in:
	issue7921.go:45: bufferNoEscape4 b does not escape
issue7921.go:49: no match for `inlining call` in:
	issue7921.go:49: make([]byte, 0, 128) escapes to heap
issue7921.go:49: no match for `make\(\[\]byte, 0, 128\) does not escape` in:
	issue7921.go:49: make([]byte, 0, 128) escapes to heap
issue7921.go:49: no match for `&bytes.Buffer literal does not escape` in:
	issue7921.go:49: make([]byte, 0, 128) escapes to heap
Unmatched Errors:
issue7921.go:25: make([]byte, 0, 64) escapes to heap
issue7921.go:33: make([]byte, 0, 64) escapes to heap
issue7921.go:49: make([]byte, 0, 128) escapes to heap

FAIL	fixedbugs/issue7921.go	0.047s
2018/09/24 17:35:33 Failed: exit status 1
2018/09/24 17:35:33 FAILED

Maybe we do want https://go-review.googlesource.com/c/go/+/136898 after all.

/cc @ALTree

[ALTree]

This is #27833

[ALTree]

The underlying issue is likely the same (issue7921.go has an external dep on the bytes package). At this point I agree we may want a way to skip tests on noopt with a tag.

[bradfitz]

Closing in favor of #27833