cmd/compilebench: use -a instead of -i to ensure dependencies are built
cmd/compilebench: use -a instead of -i to ensure dependencies are built

-i has been deprecated since 1.15, and is now gone in the soon-to-be-1.20.

Change-Id: Ib570f2bcfd0b1feb937990b72e4c9e43e1ada8cd
Reviewed-on: https://go-review.googlesource.com/c/tools/+/443456
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: David Chase <ae171625adc8645b8b79b7e405a6da5aba5341e0@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@google.com>
Run-TryBot: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools