Use versioned shared library names.

crbug.com/336438
diff --git a/src/Reactor/Nucleus.cpp b/src/Reactor/Nucleus.cpp
index fec9421..c5377a8 100644
--- a/src/Reactor/Nucleus.cpp
+++ b/src/Reactor/Nucleus.cpp
@@ -34,7 +34,7 @@
 
 #include <fstream>
 
-#if defined(__x86_64__)
+#if defined(__x86_64__) && defined(_WIN32)
 extern "C" void X86CompilationCallback()
 {
 	assert(false);   // UNIMPLEMENTED