[3p][go][build] Use embed instead of library

... in go_binary and go_test targets.

This prepares GN Go targets for the Bazel migration, nudging them to be
more consistent with how Bazel defines Go targets.

Bug: 481921739
Change-Id: I6a0d67e5263f14a45d57a0b5b1d08baa308acfd8
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/go/+/1495876
Reviewed-by: David Turner <digit@google.com>
Commit-Queue: Jay Zhuang <jayzhuang@google.com>

makeroot/BUILD.gn

diff --git a/makeroot/BUILD.gn b/makeroot/BUILD.gn
index 2b6b544..301d5ae 100644
--- a/makeroot/BUILD.gn
+++ b/makeroot/BUILD.gn
@@ -21,7 +21,7 @@
   }
 
   go_test("makeroot_test") {
-    library = ":makeroot_lib"
+    embed = [ ":makeroot_lib" ]
     output_name = "makeroot_test"
   }