Subzero: Fix Makefile.standalone to enable format with --host-flavor=debug flag

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> LIBCXX_INSTALL_PATH=<path> CLANG_PATH=<path> \
 #        PNACL_BIN_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 201 matching lines @@
   # LLVM cmake build
   LLVM_LIBS := $(LLVM_LIBS_LIST)
   # For the cmake build, the gtest libs end up in the same place as the LLVM
   # libs, so no "-L..." arg is needed.
   GTEST_LIB_PATH ?=
   CLANG_FORMAT_PATH ?= $(PNACL_BIN_PATH)
 else
   # LLVM autoconf build
   LLVM_LIBS := -lLLVM-3.7svn
   GTEST_LIB_PATH ?= -L../../out/llvm_x86_64_linux_work/Release+Asserts/lib
-  CLANG_FORMAT_PATH ?= ../../out/llvm_x86_64_linux_work/Release+Asserts/bin
+  ifneq ($(wildcard ../../out/llvm_x86_64_linux_work/Release+Asserts/bin/clang-format),)
+    CLANG_FORMAT_PATH ?= ../../out/llvm_x86_64_linux_work/Release+Asserts/bin
+  else
+    CLANG_FORMAT_PATH ?= ../../out/llvm_x86_64_linux_debug_work/Debug+Asserts/bin
+  endif
 endif
 
 LLVM_LDFLAGS := $(LLVM_LIBS) \
                 `$(PNACL_BIN_PATH)/llvm-config --ldflags` \
                 `$(PNACL_BIN_PATH)/llvm-config --system-libs`
 SB_LLVM_LDFLAGS := -Wl,--start-group $(LLVM_LIBS_LIST) -Wl,--end-group \
                    -L$(SB_LLVM_PATH)/lib
 
 CCACHE := `command -v ccache`
 CXX := CCACHE_CPP2=yes $(CCACHE) $(CLANG_PATH)/clang++
@@ skipping 549 matching lines @@
 
 help-check-xtest:
         @cat Makefile.standalone-help/check-xtest.txt
 
 clean:
         rm -rf pnacl-sz *.o $(foreach nexe,$(NEXES),$(notdir $(nexe))) \
           $(OBJDIR) $(SB_OBJDIR) $(SBB_OBJDIR) build/*.bloat.json
 
 clean-all: clean
         rm -rf build/ crosstest/Output/