Disable Subzero IR generation for performance testing.

Makefile.standalone

 # The following variables will likely need to be modified, depending on where
 # and how you built LLVM & Clang. They can be overridden in a command-line
 # invocation of make, like:
 #
 #   make LLVM_SRC_PATH=<path> LLVM_BIN_PATH=<path> \
 #        LIBCXX_INSTALL_PATH=<path> CLANG_PATH=<path> ...
 #
 
 # LLVM_SRC_PATH is the path to the root of the checked out source code. This
 # directory should contain the configure script, the include/ and lib/
@@ skipping 33 matching lines @@
   OBJDIR = build/Release
   OPTLEVEL = -O2
 endif
 
 # The list of CXX defines that are dependent on build parameters.
 CXX_DEFINES =
 
 ifdef MINIMAL
   OBJDIR := $(OBJDIR)+Min
   CXX_DEFINES += -DALLOW_TEXT_ASM=0 -DALLOW_DUMP=0 -DALLOW_LLVM_CL=0 \
-                 -DALLOW_LLVM_IR=0 -DALLOW_LLVM_IR_AS_INPUT=0
+                 -DALLOW_LLVM_IR=0 -DALLOW_LLVM_IR_AS_INPUT=0 \
+                 -DALLOW_DISABLE_IR_GEN=0
 else
   CXX_DEFINES += -DALLOW_TEXT_ASM=1 -DALLOW_DUMP=1 -DALLOW_LLVM_CL=1 \
-                 -DALLOW_LLVM_IR=1 -DALLOW_LLVM_IR_AS_INPUT=1
+                 -DALLOW_LLVM_IR=1 -DALLOW_LLVM_IR_AS_INPUT=1 \
+                 -DALLOW_DISABLE_IR_GEN=1
 endif
 
 ifdef NOASSERT
   ASSERTIONS = -DNDEBUG
 else
   ASSERTIONS =
   OBJDIR := $(OBJDIR)+Asserts
 endif
 
 $(info -----------------------------------------------)
@@ skipping 106 matching lines @@
 endif
 format-diff:
         git diff -U0 `git merge-base HEAD master` | \
         $(CLANG_FORMAT_DIFF) -p1 -style=LLVM -i
 
 clean:
         rm -rf llvm2ice *.o $(OBJDIR)
 
 clean-all: clean
         rm -rf build/