Ensure getConstString uses slow path for non-image compilation

Change-Id: If7f0eeb277e1ddc9028c90d4b8fab1621f1ea77e
diff --git a/src/compiler/Frontend.cc b/src/compiler/Frontend.cc
index d0c92f6..33dbba4 100644
--- a/src/compiler/Frontend.cc
+++ b/src/compiler/Frontend.cc
@@ -711,6 +711,7 @@
     oatInit(compiler);
 
     memset(&cUnit, 0, sizeof(cUnit));
+    cUnit.compiler = &compiler;
     cUnit.method = method;
     cUnit.instructionSet = (OatInstructionSetType)insnSet;
     cUnit.insns = code_item->insns_;