[RFCLAT#15] Static link libc++

Static link libc++ can save the apex size 700KiB+ (libc++.so).

before:
$ deapexer extract out/target/product/raven/system/apex/com.google.android.tethering.apex apex_default
$ ls -all out/target/product/raven/system/apex/com.google.android.tethering.apex
-rw-r--r-- 1 nuccachen primarygroup 3719168 Jan  5 18:40 out/target/product/raven/system/apex/com.google.android.tethering.apex

after:
$ deapexer extract out/target/product/raven/system/apex/com.google.android.tethering.apex apex_stl_static
$ ls -all out/target/product/raven/system/apex/com.google.android.tethering.apex
-rw-r--r-- 1 nuccachen primarygroup 2998272 Jan  6 22:50 out/target/product/raven/system/apex/com.google.android.tethering.apex

libc++.so is removed from the apex which uses clatd with static link
libc++:
$ diff -r apex_default/ apex_stl_static/
Only in apex_default/lib64: libc++.so

$ ls -all apex_default/lib64/libc++.so
-rw-r--r-- 1 nuccachen primarygroup 716664 Jan  1  1970 libc++.so

Bug: 212345928
Bug: 213123047
Test: atest clatd_test
Change-Id: I7f71eac09e659355781ecd275fcc70bef262f3d0
diff --git a/Android.bp b/Android.bp
index 4e3c162..3ef0115 100644
--- a/Android.bp
+++ b/Android.bp
@@ -68,6 +68,10 @@
         "liblog",
     ],
 
+    // Static libc++ for smaller apex size while shipping clatd in the mainline module.
+    // See b/213123047
+    stl: "libc++_static",
+
     // Only enable clang-tidy for the daemon, not the tests, because enabling it for the
     // tests substantially increases build/compile cycle times and doesn't really provide a
     // security benefit.