Enhance build process

Summary:
After building yoga aar, we found several issues:
1. More dynamic so files. This is bad as lower-end Android devices cannot load that many sos.
2. Size increase.
3. (Minor) The libs are stored in asset folder rather than "libs/".

We apply the following optimizations:
1. Remove dependency on memalign16 (this is brought in by a pure header dependency jni-hack);
2. Enable native relinker to remove unused symbols in the so files.
3. Link yogacore statically to reduce size churn.

Differential Revision: D20808623

fbshipit-source-id: dfbf86525bd90a097348a15a663db2381ade3ba3

java/BUCK

@@ -7,7 +7,7 @@ load("//tools/build_defs/oss:yoga_defs.bzl", "ANDROID", "CXX_LIBRARY_WHITELIST",
 
 CXX_LIBRARY_WHITELIST_FOR_TESTS = CXX_LIBRARY_WHITELIST + [
     yoga_cxx_lib("testutil:jni"),
-    yoga_cxx_lib("testutil:testutil"),
+    yoga_cxx_lib("testutil:testutil-jni"),
 ]
 
 YOGA_JAVA_IMPLEMENTATION_FILES = [
@@ -54,7 +54,7 @@ yoga_cxx_library(
     visibility = ["PUBLIC"],
     deps = [
         JNI_TARGET,
-        yoga_dep(":yoga"),
+        yoga_dep(":yoga-static"),
         ":ndklog",
     ],
 )