Add libwinpthread-1.dll to windows sdk, copied from clang-r365631b am: 67595976c2 am: 45d357a83a am: 7e278b2ca0

Original change: https://googleplex-android-review.googlesource.com/c/platform/prebuilts/sdk/+/10486797

Change-Id: I653cfea2653c3f209ab3bbe42da21dbfc0bda86c