add: user library and some applications

user/Makefile

@@ -0,0 +1,18 @@
+TARGET := riscv64gc-unknown-none-elf
+MODE := release
+APP_DIR := src/bin
+TARGET_DIR := target/$(TARGET)/$(MODE)
+APPS := $(wildcard $(APP_DIR)/*.rs)
+ELFS := $(patsubst $(APP_DIR)/%.rs, $(TARGET_DIR)/%, $(APPS))
+BINS := $(patsubst $(APP_DIR)/%.rs, $(TARGET_DIR)/%.bin, $(APPS))
+
+OBJDUMP := rust-objdump --arch-name=riscv64
+OBJCOPY := rust-objcopy --binary-architecture=riscv64
+
+elf:
+	@cargo build --release
+
+binary: elf
+	@$(foreach elf, $(ELFS), $(OBJCOPY) $(elf) --strip-all -O binary $(patsubst $(TARGET_DIR)/%, $(TARGET_DIR)/%.bin, $(elf));)
+
+build: binary