goldfish-opengl: add cstring in various places

Helps with the g++ build.  Also, remove $(LINUX_GUEST_BUILD)
guard since it's not useful.

BUG=202552093
TEST=compile

Change-Id: I40680660a3f2b4da97be61c8b827cd20b087ea95
diff --git a/system/vulkan_enc/func_table.cpp b/system/vulkan_enc/func_table.cpp
index a27e40f..cde7e0b 100644
--- a/system/vulkan_enc/func_table.cpp
+++ b/system/vulkan_enc/func_table.cpp
@@ -32,6 +32,7 @@
 #include "goldfish_vk_private_defs.h"
 
 #include <log/log.h>
+#include <cstring>
 
 // Stuff we are not going to use but if included,
 // will cause compile errors. These are Android Vulkan