Dont's pass enable-libcpp to build (host) tools when cross-compiling with libcpp

Our cross-build (i.e. the sandboxed translator build) still uses libcpp but the host
build does not.

This goes along with https://chromium-review.googlesource.com/c/native_client/src/native_client/+/2093138
to stop using libcxx in the LLVM host build

Change-Id: Ifc96c80b854e76b0482a7c538c784d12b0c9fabc
Bug: https://bugs.chromium.org/p/nativeclient/issues/detail?id=4421
Reviewed-on: https://chromium-review.googlesource.com/c/native_client/pnacl-llvm/+/2189571
Reviewed-by: Derek Schuff <dschuff@chromium.org>
diff --git a/Makefile b/Makefile
index e9559af..d8546d6 100644
--- a/Makefile
+++ b/Makefile
@@ -128,9 +128,6 @@
 	  unset SDKROOT ; \
 	  unset UNIVERSAL_SDK_PATH ; \
 	  configure_opts= ; \
-	  if test "$(ENABLE_LIBCPP)" -ne 0 ; then \
-	    configure_opts="$$configure_opts --enable-libcpp"; \
-	  fi; \
 	  $(PROJ_SRC_DIR)/configure --build=$(BUILD_TRIPLE) \
 		--host=$(BUILD_TRIPLE) --target=$(BUILD_TRIPLE) \
 	        --disable-polly $$configure_opts; \
@@ -150,7 +147,6 @@
 	  ENABLE_COVERAGE=$(ENABLE_COVERAGE) \
 	  DISABLE_ASSERTIONS=$(DISABLE_ASSERTIONS) \
 	  ENABLE_EXPENSIVE_CHECKS=$(ENABLE_EXPENSIVE_CHECKS) \
-	  ENABLE_LIBCPP=$(ENABLE_LIBCPP) \
 	  CC=$(BUILD_CC) \
 	  CXX=$(BUILD_CXX) \
 	  CFLAGS="$(BUILD_CFLAGS)" \