cmd/go: overwrite program name with full path
cmd/go: overwrite program name with full path

If the program path is resolved, replace the first argument of the
exec.Cmd, which is the bare program name with the resolved path.

Change-Id: I92cf5e6f4bb7c8fef9b59f5eab963f4e75b90d07
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/957908
Reviewed-by: Katie Hockman <b67e673702df165eba99d19477fbb63eec0d8851@google.com>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@google.com>
Reviewed-by: Jay Conrod <f3fadaedc813344da5ec13b41e26596889cc5baa@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/284784
Trust: Roland Shoemaker <0d270388f2f92757a5de0f4bd891d3b392c44c4f@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Roland Shoemaker <0d270388f2f92757a5de0f4bd891d3b392c44c4f@golang.org>

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