all: check GOROOT_BOOTSTRAP executable before bootsrappping
all: check GOROOT_BOOTSTRAP executable before bootsrappping

Otherwise we’d still be writing that we're building cmd/dist
even if GOROOT_BOOTSTRAP we’re wrongly set.

Change-Id: I940e18c3cebae5664f85babc9919e9eb215d5093
Reviewed-on: https://go-review.googlesource.com/c/go/+/253877
Run-TryBot: Cuong Manh Le <54b4457f1dff6823379654eb5867596497ba782f@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Emmanuel Odeke <277f8eaa8c7dfbc55c17bf5e30561c1a9c45c569@gmail.com>

CAFxX/go,nawawi/go,golang/go,golang/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,cloudflare/go,golang/go,cloudflare/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,golang/go