Look for the compiler directly, not just the existence of the
directory containing.
Fixesgolang/go#30637
Change-Id: Iae4429406da8622e7085bf3701c0f84d5c95d2fd
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/165937
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>