Refactor the compilers out of libart.

This builds three separate compilers and dynamically links with the right one
at runtime.

Change-Id: I59d22b9884f41de733c09f97e29ee290236d5f4b
diff --git a/src/compiler/CompilerIR.h b/src/compiler/CompilerIR.h
index 6bda522..2515713 100644
--- a/src/compiler/CompilerIR.h
+++ b/src/compiler/CompilerIR.h
@@ -307,7 +307,7 @@
     bool methodTraceSupport;            // For TraceView profiling
     struct RegisterPool* regPool;
     int optRound;                       // round number to tell an LIR's age
-    OatInstructionSetType instructionSet;
+    InstructionSet instructionSet;
     /* Number of total regs used in the whole cUnit after SSA transformation */
     int numSSARegs;
     /* Map SSA reg i to the Dalvik[15..0]/Sub[31..16] pair. */