Mark libF77blas as vendor_available

This is required by libblas, which is a vndk-sp library. Since this is a
static library, vendor_available: true is enough.

Bug: 64425518
Bug: 64395154
Test: BOARD_VNDK_VERSION=current m -j libblas.vendor

Merged-In: I496a1f150719c15ac1c50508ebf9a097c5630347
Change-Id: I496a1f150719c15ac1c50508ebf9a097c5630347
(cherry picked from commit aaa7c2fb)