Build curl as shared library

Change-Id: I7b2c8b4491c8d84ef1db8cfeda18bd12061ba91a
diff --git a/BUILD.gn b/BUILD.gn
index 3767f07..f31e6f2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -54,7 +54,7 @@
   ]
 }
 
-static_library("libcurl") {
+shared_library("libcurl") {
   sources = [
     "lib/amigaos.c",
     "lib/amigaos.h",
@@ -304,6 +304,7 @@
   ]
   defines = [
     "BUILDING_LIBCURL",
+    "CURL_HIDDEN_SYMBOLS",
     "HAVE_CONFIG_H",
   ]
   include_dirs = [ "lib" ]