How can I divide the driver file into two source files without having multiple definitions error?

I wrote a simple GPIO driver for Nucleo-l432kc board I used one GPIO.c file and multiple headers for RCC GPIO ..etc

I added the main method in the same file GPIO.c and it worked fine

now I moved the main function to another file main.c (to isolate the example and the driver code) but now I got multiple definitions linker error when trying to link main.o and GPIO.o so how I can compile multiple source files and avoid this linker error ?

GPIO.c:

#include <GPIO.h>
 
 
 
uint8_t gpio_read_pin(GPIO_TypeDef *GPIOx, uint8_t pin){
	return ((GPIOx->IDR & (1 << pin)) ? 1 : 0);
}
void gpio_write_pin(GPIO_TypeDef *GPIOx, uint8_t pin, uint8_t value){
	if(value) 	GPIOx->ODR |= (1 << pin) ;
	else 		GPIOx->ODR &= ~(1 << pin);
}
void gpio_set_alt_func(GPIO_TypeDef *GPIOx, uint8_t pin, uint8_t alt_fun){
	uint8_t baseBit = (pin * 4) % 32;
	uint8_t reg = pin < 8 ? 0 : 1;
 
	GPIOx->AFR[reg] &= ~(0b1111 << baseBit);
	GPIOx->AFR[reg] |= (alt_fun << baseBit);
}
static void gpio_configure_pin_mode(GPIO_TypeDef *GPIOx, uint8_t pin, uint32_t mode){
	GPIOx->MODER &= ~(3 << (pin * 2));
	GPIOx->MODER |= (mode << (pin * 2));
}
static void gpio_configure_pin_otype(GPIO_TypeDef *GPIOx, uint8_t pin, uint32_t op_type){
	GPIOx->OTYPER &= ~(1 << pin);
	GPIOx->OTYPER |= (op_type << pin);
}
static void gpio_configure_pin_ospeed(GPIO_TypeDef *GPIOx, uint8_t pin, uint32_t ospeed){
	GPIOx->OSPEEDR &= ~(3 << (pin * 2));
	GPIOx->OSPEEDR |= (ospeed << (pin * 2));
}
static void gpio_configure_pin_pupd(GPIO_TypeDef *GPIOx, uint8_t pin, uint32_t pupd){
	GPIOx->PUPDR &= ~(3 << (pin * 2));
	GPIOx->PUPDR |= (pupd << (pin * 2));
}
 
void gpio_init(GPIO_TypeDef* GPIOx, gpio_pin_conf_t* pin_conf){
	//first configure the mode
	gpio_configure_pin_mode(GPIOx, pin_conf->pin, pin_conf->mode);
	//configure the output type
	gpio_configure_pin_otype(GPIOx, pin_conf->pin, pin_conf->op_type);
	//configure the ospeed
	gpio_configure_pin_ospeed(GPIOx, pin_conf->pin, pin_conf->speed);
	//configure the alternate function
	if(pin_conf->alternate_function != -1)
		gpio_set_alt_func(GPIOx, pin_conf->pin, pin_conf->alternate_function);
}

main.c:

#include <GPIO.h>
#include <RCC.h>
 
int main(){
	gpio_pin_conf_t led;
	led.pin = A1;
	led.mode = GPIO_PIN_OUTPUT_MODE;
	led.op_type = GPIO_PIN_OP_TYPE_PUSH_PULL;
	led.speed = GPIO_PIN_OSPEED_LOW;
	led.alternate_function = -1;
 
	RCC_GPIOA_CLK_ENABLE();
	gpio_init(GPIOA, &led);
 
	uint32_t state = GPIO_OUTPUT_LOW; 
	while(1){
		for(int i = 0; i < 100000; i++);
		gpio_write_pin(GPIOA, led.pin, state);
		state = !state;
	}
	return 0;
}

Makfile:

projectName = GPIO
TOOLCHAIN = /home/mahmoud/arm-gnu-toolchain-12.2.rel1-x86_64-arm-none-eabi/bin
 
all: compile link upload
 
compile: src/$(projectName).c 
	$(TOOLCHAIN)/arm-none-eabi-gcc -g -c -mcpu=cortex-m4 -mthumb src/main.c -o Build/main.o -I ../include/
	$(TOOLCHAIN)/arm-none-eabi-gcc -g -c -mcpu=cortex-m4 -mthumb src/$(projectName).c -o Build/$(projectName).o -I ../include/
 
assemble:
	$(TOOLCHAIN)/arm-none-eabi-as -g -mcpu=cortex-m4 -mthumb ../startup/startup_stm32l432xx.s -o Build/startup_stm32l432xx.o
 
link:	compile	assemble
	$(TOOLCHAIN)/arm-none-eabi-ld Build/*.o -o Build/$(projectName).elf -T ../linker/STM32L432KCUx_FLASH.ld
 
upload:	link
	openocd -f interface/stlink.cfg -f target/stm32l4x.cfg -c "program Build/$(projectName).elf verify reset exit"

errors:

/home/mahmoud/arm-gnu-toolchain-12.2.rel1-x86_64-arm-none-eabi/bin/arm-none-eabi-ld: Build/main.o:/home/mahmoud/code/Nucleo-L432kc/GPIO/../include/stm32l432kc.h:280: multiple definition of `RCC'; Build/GPIO.o:/home/mahmoud/code/Nucleo-L432kc/GPIO/../include/stm32l432kc.h:280: first defined here