Updated: Now that we have a modern Go toolchain available, we should build with Go 1.10.1 (latest we have on all platforms).  This includes updating Go used on arm64.  We can also drop GOROOT as that's now computed relative to the go binary in Go 1.10 and later.

Original: On arm64, mongorestore tests provoke a panic when run with Go 1.7 and Go 1.8. The issues does not occur with gccgo 1.4 or Go 1.9/1.10. For now, we're building tools on arm64 with gcc go. When Go 1.9 or later is available in our build toolchain, we should upgrade the build to a recent Go version.