Fix the build

Change-Id: I17bb89c51b1d4231a3cec3b91b453583e872d1b2

poincare/Makefile

@@ -42,9 +42,10 @@ tests += $(addprefix poincare/test/,\
   subtraction.cpp\
 )
 
-# We won't use this very often but the linker should be smart enough to just
-# remove it if we don't use it.
+ifdef POINCARE_TESTS_PRINT_EXPRESSIONS
 tests += poincare/src/expression_debug.o
+SFLAGS += -DPOINCARE_TESTS_PRINT_EXPRESSIONS=1
+endif
 
 # Even though flex and bison will generate both implementation and headers at
 # once, we don't declare it in the Makefile. If we did, "make -jN" with N>1 may

poincare/test/simplify_addition_integer.cpp

@@ -2,8 +2,7 @@
 #include <poincare.h>
 #include <assert.h>
 
-#define DUMP_EXPRESSIONS_TO_STD_OUT 1
-#if DUMP_EXPRESSIONS_TO_STD_OUT
+#if POINCARE_TESTS_PRINT_EXPRESSIONS
 #include "../src/expression_debug.h"
 #include <iostream>
 using namespace std;