ExpressionParser: only force link MCJIT when needed

This was added to support FreeBSD.  The inclusion of this header increases the
size of `lldb-server` due to MCJIT being forcefully preserved.  Conditionalise
the inclusion to shared builds of LLVM which will allow for MCJIT to be stripped
if unnecessary when performing static linking of tools.  This shaves off ~28% of
the binary size for lldb-server when linked with gold using
`-ffunction-sections` and `-fdata-sections`.

llvm-svn: 359944
diff --git a/lldb/source/API/SystemInitializerFull.cpp b/lldb/source/API/SystemInitializerFull.cpp
index 8e5e1a8..6566f08 100644
--- a/lldb/source/API/SystemInitializerFull.cpp
+++ b/lldb/source/API/SystemInitializerFull.cpp
@@ -114,6 +114,11 @@
 
 #include "llvm/Support/TargetSelect.h"
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wglobal-constructors"
+#include "llvm/ExecutionEngine/MCJIT.h"
+#pragma clang diagnostic pop
+
 #include <string>
 
 using namespace lldb_private;