build: implement platform-agnostic build system

- Split Makefile into gmake.mk (Linux/Windows) and bmake.mk (BSD/macOS)
- Added config.mk for shared variables.
- Added build.sh and build.bat dispatchers.
- Retains old build behavior with dependency tracking.

gmake.mk

@@ -0,0 +1,43 @@
+include config.mk
+
+ifeq ($(OS),Windows_NT)
+    FULL_LIB := $(LIB_NAME).dll
+    LDFLAGS_PLAT := -ldl
+else
+    FULL_LIB := lib$(LIB_NAME).so
+    LDFLAGS_PLAT := -ldl
+    CFLAGS_PLAT := -fPIC
+endif
+
+CFLAGS_BASE := -Wall -Wpedantic -I$(INC_DIR) -std=c89 $(CFLAGS_PLAT)
+
+.PHONY: all debug release clean
+
+all: debug
+
+debug: $(BIN_DIR)/debug/$(FULL_LIB)
+release: $(BIN_DIR)/release/$(FULL_LIB)
+
+# Debug Rules
+$(BIN_DIR)/debug/$(FULL_LIB): $(SRCS:src/%.c=obj/debug/%.o)
+	@mkdir -p $(@D)
+	$(CC) -shared -o $@ $^ $(LDFLAGS_PLAT)
+
+obj/debug/%.o: src/%.c
+	@mkdir -p $(@D)
+	$(CC) $(CFLAGS_BASE) -g -O0 -MMD -MP -c $< -o $@
+
+# Release Rules
+$(BIN_DIR)/release/$(FULL_LIB): $(SRCS:src/%.c=obj/release/%.o)
+	@mkdir -p $(@D)
+	$(CC) -shared -o $@ $^ $(LDFLAGS_PLAT)
+
+obj/release/%.o: src/%.c
+	@mkdir -p $(@D)
+	$(CC) $(CFLAGS_BASE) -O2 -MMD -MP -c $< -o $@
+
+-include $(wildcard obj/debug/*.d)
+-include $(wildcard obj/release/*.d)
+
+clean:
+	rm -rf $(OBJ_DIR) $(BIN_DIR)