Turn off dump/emit routines when building minimal subzero.

Remove the dump/emit routines when ALLOW_DUMP=0. Also fixes some
verbosity messages to not print if ALLOW_DUMP=0. Note: emit routines
needed for emitIAS are not turned off.

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/686913005
diff --git a/Makefile b/Makefile
index 47a48fd..49161dd 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,6 @@
 
 CXX.Flags += -std=c++11
 
-CPP.Defines += -DALLOW_TEXT_ASM=1 -DALLOW_DUMP=1 -DALLOW_LLVM_CL=1 \
-               -DALLOW_LLVM_IR=1 -DALLOW_LLVM_IR_AS_INPUT=1
+CPP.Defines += -DALLOW_DUMP=1 -DALLOW_LLVM_CL=1 -DALLOW_LLVM_IR=1 \
+	-DALLOW_LLVM_IR_AS_INPUT=1 -DALLOW_DISABLE_IR_GEN=1