[sdk] Define a publication category for prebuilt shared libs.

DX-89

Change-Id: I914a2fa1374c390305c366e3b7570339015a800a
diff --git a/BUILD.gn b/BUILD.gn
index 377bf2f..a51b784 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -27,6 +27,9 @@
 # libcrypto.so #
 ################
 target(library_type, "crypto") {
+  if (is_fuchsia) {
+    category = "partner"
+  }
   sources = crypto_sources
   public = crypto_headers
   public_configs = [ ":boringssl_config" ]
@@ -68,6 +71,9 @@
 }
 
 target(library_type, "ssl") {
+  if (is_fuchsia) {
+    category = "partner"
+  }
   sources = ssl_sources
   public = ssl_headers
   public_configs = [ ":boringssl_config" ]