Fix cmake build

Bug: 171711491

X11Support.cpp was not being built.

Change-Id: I353b77844ee17c79f84319feb249768fdce9d409
diff --git a/stream-servers/apigen-codec-common/X11Support.cpp b/stream-servers/apigen-codec-common/X11Support.cpp
index e4a5787..eedf92f 100644
--- a/stream-servers/apigen-codec-common/X11Support.cpp
+++ b/stream-servers/apigen-codec-common/X11Support.cpp
@@ -70,12 +70,12 @@
         GlxApi mApi;
 };
 
-struct X11Api* getX11Api() {
+AEMU_EXPORT struct X11Api* getX11Api() {
     static X11FunctionGetter* g = new X11FunctionGetter;
     return g->getApi();
 }
 
-struct GlxApi* getGlxApi() {
+AEMU_EXPORT struct GlxApi* getGlxApi() {
     static GlxFunctionGetter* g = new GlxFunctionGetter;
     return g->getApi();
 }