[build] Mark curl shell=true instead of deprecated_system_image

Change-Id: I5353704f591e69bbf7161db5e458c1184765a488
diff --git a/BUILD.gn b/BUILD.gn
index 7de5144..1b5e0f6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -29,8 +29,6 @@
 import("//build/package.gni")
 
 package("curl") {
-  deprecated_system_image = true
-
   deps = [
     ":curl_bin",
   ]
@@ -38,6 +36,7 @@
   binaries = [
     {
       name = "curl"
+      shell = true
     },
   ]
 }