Also weaken `__floattidf`

Fixes link error with ion shell.

Makefile

@@ -113,7 +113,7 @@ $(BUILD)/debug/libc.so: $(BUILD)/debug/librelibc.a $(BUILD)/pthreads-emb/libpthr
 $(BUILD)/debug/librelibc.a: $(SRC)
 	CARGO_INCREMENTAL=0 $(CARGO) rustc $(CARGOFLAGS) -- --emit link=$@ $(RUSTCFLAGS)
 	# FIXME: Remove the following line. It's only required since xargo automatically links with compiler_builtins, which conflicts with the compiler_builtins that rustc always links with.
-	$(OBJCOPY) $@ -W __divti3 -W __muloti4 -W __udivti3
+	$(OBJCOPY) $@ -W __divti3 -W __muloti4 -W __udivti3 -W __floattidf
 	touch $@
 
 $(BUILD)/debug/crt0.o: $(SRC)
@@ -152,7 +152,7 @@ $(BUILD)/release/libc.so: $(BUILD)/release/librelibc.a $(BUILD)/pthreads-emb/lib
 $(BUILD)/release/librelibc.a: $(SRC)
 	CARGO_INCREMENTAL=0 $(CARGO) rustc --release $(CARGOFLAGS) -- --emit link=$@ $(RUSTCFLAGS)
 	# FIXME: Remove the following line. It's only required since xargo automatically links with compiler_builtins, which conflicts with the compiler_builtins that rustc always links with.
-	$(OBJCOPY) $@ -W __divti3 -W __muloti4 -W __udivti3
+	$(OBJCOPY) $@ -W __divti3 -W __muloti4 -W __udivti3 -W __floattidf
 	touch $@
 
 $(BUILD)/release/crt0.o: $(SRC)