cmd/go: GO15VENDOREXPERIMENT=1 breaks 'go run x.go'

[capnm]

It took me a while to figure out what's going on.

ok      regexp/syntax   1.093s
--- FAIL: TestCgoCrashHandler (0.10s)
    crash_test.go:85: building source: exit status 1
        invalid vendoredImportPath: dir="/tmp/go-build823840384" root="." separator="/"
--- FAIL: TestCgoSignalDeadlock (0.03s)
    crash_test.go:85: building source: exit status 1
        invalid vendoredImportPath: dir="/tmp/go-build849881567" root="." separator="/"
--- FAIL: TestCgoTraceback (0.02s)

etc.

[capnm]

It breaks go run/build etc. outside or without the $GOPATH/src/*/:

cd /tmp
unset GOPATH
$ go run t.go 
invalid vendoredImportPath: dir="/tmp" root="." separator="/"