diff --git a/config/mt-ospace b/config/mt-ospace
new file mode 100644
index 00000000000..7f091041d8a
--- /dev/null
+++ b/config/mt-ospace
@@ -0,0 +1,3 @@
+# Build libraries optimizing for space, not speed.
+ CFLAGS_FOR_TARGET = -g -Os
+ CXXFLAGS_FOR_TARGET = -g -Os