use a script to output zero-terminated strings instead of bash printf

Makefile

@@ -607,6 +607,7 @@ EMU_FLAGS = --noosd
 LOADER = loader64
 LOADER_FLAGS = -vwf
 SHA1SUM = sha1sum
+ZEROTERM = $(PYTHON) $(TOOLS_DIR)/zeroterm.py
 
 ###################### Dependency Check #####################
 
@@ -725,7 +726,7 @@ endif
 # RGBA32, RGBA16, IA16, IA8, IA4, IA1, I8, I4
 ifeq ($(EXTERNAL_TEXTURES),1)
 $(BUILD_DIR)/%: %.png
-	printf "%s%b" "$(patsubst %.png,%,$^)" '\x00' > $@
+	$(ZEROTERM) "$(patsubst %.png,%,$^)" > $@
 else
 $(BUILD_DIR)/%: %.png
 	$(N64GRAPHICS) -i $@ -g $< -f $(lastword $(subst ., ,$@))

tools/zeroterm.py

@@ -0,0 +1,6 @@
+#!/usr/bin/env python3
+import sys
+if len(sys.argv) < 2:
+    print("usage: zeroterm <string>")
+else:
+    sys.stdout.buffer.write(bytes(sys.argv[1], 'ascii') + b'\x00')