Revert of Remove rt flags that are not necessary (patchset #1 id:1 of https://coderev...

Revert of Remove rt flags that are not necessary (patchset #1 id:1 of https://codereview.chromium.org/1226123012/)

Reason for revert:
breaks tests, e.g.
https://build.chromium.org/p/client.skia.android/builders/Test-Android-GCC-Nexus9-GPU-TegraK1-Arm64-Release/builds/752/steps/dm/logs/stdio

Original issue's description:
> Remove rt flags that are not necessary
>
> Committed: https://skia.googlesource.com/skia/+/b6b0a6ef179f4143c94ba7e0e1be6e7ce4b0a23a

TBR=joshualitt@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1234503004