Mark release builds as betas, not stable. am: 52de48469c am: fd22786a98 am: 879f825331 am: 87f0c5bc0e

Original change: https://android-review.googlesource.com/c/platform/tools/ndkports/+/1905930

Change-Id: I3a0bfc1917d918206807c26038d103ccb15eea2f