Move RunLoop test class to its own build target

To make it usable in tests without depending on all of CallTest.

Bug: None
Change-Id: Ie3102ab71bcfe3862dd6c35d3285098e961e54df
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262807
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36932}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index e02f8d9..edaaa8b 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -260,6 +260,7 @@
       "../test:fake_video_codecs",
       "../test:null_transport",
       "../test:rtp_test_utils",
+      "../test:run_loop",
       "../test:run_test",
       "../test:run_test_interface",
       "../test:test_common",