Clarify documentation about running binaries

The requirement for target documentation talks about "running tests",
but tier 3 targets often don't support running the full testsuite, and
in practice the documentation for how to run an individual binary may be
more useful. Change "running tests" to "running binaries, or running
tests".

Author: joshtriplett

src/doc/rustc/src/target-tier-policy.md

@@ -188,9 +188,9 @@ approved by the appropriate team for that shared code before acceptance.
   target not implementing those portions.
 - The target must provide documentation for the Rust community explaining how
   to build for the target, using cross-compilation if possible. If the target
-  supports running tests (even if they do not pass), the documentation must
-  explain how to run tests for the target, using emulation if possible or
-  dedicated hardware if necessary.
+  supports running binaries, or running tests (even if they do not pass), the
+  documentation must explain how to run such binaries or tests for the target,
+  using emulation if possible or dedicated hardware if necessary.
 - Tier 3 targets must not impose burden on the authors of pull requests, or
   other developers in the community, to maintain the target. In particular,
   do not post comments (automated or manual) on a PR that derail or suggest a