Make libwinpthread a prebuilt_cc_library_static am: a6fee370be am: e1994880d0

Original change: https://android-review.googlesource.com/c/platform/prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8/+/1950276

Change-Id: I30e5bc4a284bfd747a22b984dad01b5c44f8e6ba