Disable troublesome Mac build.

We've stopped building the libraries that depended on this for the Mac,
so now we can stop building libcurl too, making each update easier.

Bug: N/A
Test: builds
Change-Id: Icbc98f3c46d9e6b028197718e2394403f67260fe
diff --git a/Android.bp b/Android.bp
index ae5a0cc..b639598 100644
--- a/Android.bp
+++ b/Android.bp
@@ -198,6 +198,9 @@
         host: {
             cflags: ["-D_GNU_SOURCE=1"],
         },
+        darwin: {
+            enabled: false,
+        },
     },
     unique_host_soname: true,
 }