runtime: dragonfly broken by Getenv/GOROOT change

[bradfitz]

The dragonfly builder is failing with:

--- FAIL: TestGcSys (0.01s)
    crash_test.go:91: building source: exit status 1
        main.go:5:2: cannot find package "fmt" in any of:
            /usr/local/go/src/fmt (from $GOROOT)
            ($GOPATH not set)
        main.go:6:2: cannot find package "runtime" in any of:
            /usr/local/go/src/runtime (from $GOROOT)
            ($GOPATH not set)
--- FAIL: TestGCFairness (0.01s)
    crash_test.go:91: building source: exit status 1
        main.go:5:2: cannot find package "fmt" in any of:
            /usr/local/go/src/fmt (from $GOROOT)
            ($GOPATH not set)
        main.go:6:2: cannot find package "os" in any of:
            /usr/local/go/src/os (from $GOROOT)
            ($GOPATH not set)
        main.go:7:2: cannot find package "runtime" in any of:
            /usr/local/go/src/runtime (from $GOROOT)
            ($GOPATH not set)
        main.go:8:2: cannot find package "time" in any of:
            /usr/local/go/src/time (from $GOROOT)
            ($GOPATH not set)
--- FAIL: TestRuntimeGogoBytes (0.01s)
    runtime_test.go:115: building hello world: exit status 1
        package runtime: cannot find package "runtime" in any of:
            /usr/local/go/src/runtime (from $GOROOT)
            ($GOPATH not set)
--- FAIL: TestLargeStringConcat (0.02s)
    crash_test.go:91: building source: exit status 1
        package .
            imports runtime: cannot find package "runtime" in any of:
            /usr/local/go/src/runtime (from $GOROOT)
            ($GOPATH not set)
        main.go:3:8: cannot find package "strings" in any of:
            /usr/local/go/src/strings (from $GOROOT)
            ($GOPATH not set)
FAIL
FAIL    runtime 14.815s

This started at @crawshaw's:

runtime: do not share underlying envs/argv array
https://go-review.googlesource.com/#/c/6611/6

I haven't yet debugged why. Just filing this with what I've learned so far.

/cc @minux @davecheney @randall77

[crawshaw]

Another builder (the darwin ones?) broke with a similar message. I believe @davecheney found a fault in the builder binary. Installing the latest version fixed those builders.

[bradfitz]

Builder has been updated and is reported OK now.