Probleme lors de programmer Raspberry avec C

total 548
drwxr-xr-x 5 pi pi   4096 Jun 23 13:48 bcm2835-1.38
-rw-r--r-- 1 pi pi 248520 Nov 20  2014 bcm2835-1.38.tar.gz
drwxr-xr-x 5 pi pi   4096 Jun 23 23:27 bcm2835-1.52
-rw-r--r-- 1 pi pi 258007 Mar  2 01:18 bcm2835-1.52.tar.gz
drwxr-xr-x 3 pi pi   4096 Jun 24 00:22 Desktop
drwxr-xr-x 6 pi pi   4096 Jun 22 06:00 Documents
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Downloads
-rw-r--r-- 1 pi pi    333 Jun 23 03:24 Led.py
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Music
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Pictures
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Public
drwxr-xr-x 2 pi pi   4096 Jun 22 09:34 python_games
-rw-r--r-- 1 pi pi    625 Jun 23 04:34 Simple.py
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Templates
drwxr-xr-x 2 pi pi   4096 Apr 10 10:10 Videos

#include <stdio.h>
#include <bcm2835.h>
#define LED RPI_GPIO_P1_11
int main(int argc, char **argv)
{
	if(!bcm2835_init())
	return 1;
	
	
	bcm2835_gpio_fsel(LED, BCM2835_GPIO_FSEL_OUTP);
	unsigned int del=1000;
	while(1)
	{
		bcm2835_gpio_set(LED);
		bcm2835_delay(del);
		bcm2835_gpio_clr(LED);
		bcm2835_delay(del);
		}
	
}

gcc -Wall -o "VivexProject" "VivexProject.c" (in directory: /home/pi/Desktop)
/tmp/ccVZr4Pj.o: In function `main':
VivexProject.c:(.text+0x14): undefined reference to `bcm2835_init'
VivexProject.c:(.text+0x34): undefined reference to `bcm2835_gpio_fsel'
VivexProject.c:(.text+0x44): undefined reference to `bcm2835_gpio_set'
VivexProject.c:(.text+0x4c): undefined reference to `bcm2835_delay'
VivexProject.c:(.text+0x54): undefined reference to `bcm2835_gpio_clr'
VivexProject.c:(.text+0x5c): undefined reference to `bcm2835_delay'
Compilation failed.
collect2: error: ld returned 1 exit status