Make gemmlowp header only libs vendor available.

Bug: 63905942
Test: mm
Change-Id: I81438aba6375f65c25c3ade0e3bddec53db92b9e
diff --git a/Android.bp b/Android.bp
index ac93eb2..f6d9324 100644
--- a/Android.bp
+++ b/Android.bp
@@ -14,12 +14,14 @@
 
 cc_library_headers {
     name: "libfixedpoint",
+    vendor_available: true,
     host_supported: true,
     export_include_dirs: ["fixedpoint"],
 }
 
 cc_library_headers {
     name: "libgemmlowp",
+    vendor_available: true,
     host_supported: true,
     export_include_dirs: ["public"],
 }