[dev.boringcrypto.go1.16] misc/boring: use go install cmd@latest for installing command

"go get cmd" is deprecated.

Change-Id: I2242764c79b5e4c3ff94e5323d6504b596bdc9e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/385197
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 8521d1ea346212bcdabe15b4e157b3a2f2ca95f4)
Reviewed-on: https://go-review.googlesource.com/c/go/+/385235
diff --git a/misc/boring/build.release b/misc/boring/build.release
index 46922c9..f421b12 100755
--- a/misc/boring/build.release
+++ b/misc/boring/build.release
@@ -59,9 +59,7 @@
 # Build the release tool in a temporary directory.
 dir=$(mktemp -d)
 trap "rm -rf $dir" EXIT
-export GO111MODULE=on
-export GOBIN="$dir"
-(cd "$dir"; go get golang.org/x/build/cmd/release)
+GOBIN="$dir" go install golang.org/x/build/cmd/release@latest
 
 # Build the release.
 sha() {