Make gflags vendor_available

BUG: 70485924
Test: lunch aosp_arm64_ab; m -j checkbuild starts
Change-Id: I1038b77d75dd4894b0b21f791319ae9c2673b618
diff --git a/Android.bp b/Android.bp
index 17eca53..7990b05 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,6 +1,7 @@
 cc_library_static {
     name: "libgflags",
     host_supported: true,
+    vendor_available: true,
     srcs: [
         "src/gflags.cc",
         "src/gflags_completions.cc",