Update libsodium to 1.0.20 (#4342)

packages/l/libsodium/xmake.lua

@@ -7,6 +7,7 @@ package("libsodium")
              "https://github.com/jedisct1/libsodium/releases/download/$(version)-RELEASE/libsodium-$(version).tar.gz",
              "https://github.com/jedisct1/libsodium.git")
 
+    add_versions("1.0.20", "ebb65ef6ca439333c2bb41a0c1990587288da07f6c7fd07cb3a18cc18d30ce19")
     add_versions("1.0.19", "018d79fe0a045cca07331d37bd0cb57b2e838c51bc48fd837a1472e50068bbea")
     add_versions("1.0.18", "6f504490b342a4f8a4c4a02fc9b866cbef8622d5df4e5452b46be121e46636c1")