cortex-m: remove mapfile leftovers
The linker parameter --cref prints things
to the map file if that is generated. Remove
the flag now since it goes to stdout without
mapfile.
This change belonged in commit
@@ -19,7 +19,9 @@ MODULES += os/lib/newlib
LDFLAGS += -T $(LDSCRIPT)
LDFLAGS += -Wl,--gc-sections,--sort-section=alignment
-LDFLAGS += -Wl,--cref,--no-warn-mismatch
+# The next line might be trying to avoid
+# https://sourceware.org/bugzilla/show_bug.cgi?id=28910
+LDFLAGS += -Wl,--no-warn-mismatch
OBJCOPY_FLAGS += --gap-fill 0xff
