Replace build scripts with a Makefile

Single Makefile supports native builds (pkg-config) and cross-compilation
(CROSS_COMPILE/PREFIX env vars). Fixes -Wformat-truncation and
-Wstringop-truncation warnings at -O2 by sizing current_file to match
audio_files (256) and replacing strncpy with snprintf.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,32 @@
+CC = $(CROSS_COMPILE)gcc
+
+CFLAGS  = -Wall -Wno-unused -O2
+LDLIBS  = -lSDL2 -lSDL2_image -lavformat -lavcodec -lavutil -lswresample
+
+ifdef PREFIX
+  # Cross-compile: headers and libraries live under PREFIX
+  CFLAGS += -I$(PREFIX)/include -I$(PREFIX)/include/SDL2
+  LDLIBS := -L$(PREFIX)/lib $(LDLIBS)
+else
+  # Native: use pkg-config
+  PKG_CONFIG ?= pkg-config
+  PKGS = sdl2 SDL2_image libavformat libavcodec libavutil libswresample
+  CFLAGS += $(shell $(PKG_CONFIG) --cflags $(PKGS))
+  LDLIBS  = $(shell $(PKG_CONFIG) --libs $(PKGS))
+endif
+
+BUILD_DIR = build
+TARGET    = $(BUILD_DIR)/sdlamp2
+
+.PHONY: all clean
+
+all: $(TARGET)
+
+$(TARGET): src/sdlamp2.c src/controls_png.h | $(BUILD_DIR)
+	$(CC) $(CFLAGS) -o $@ $< $(LDLIBS)
+
+$(BUILD_DIR):
+	mkdir -p $@
+
+clean:
+	rm -f $(TARGET)