title: cant use sleep() in embedded c for stm32
body: <p>I try to learn embedded c for a stm32-microcontorller. I try to wirte a easy blink program, where i use the sleep()-function.</p>
  
  <p>code:</p>
  
  <pre class="lang-c prettyprint-override"><code>/* Includes ------------------------------------------------------------------*/
  #include &lt;unistd.h&gt;
  #include "main.h"
  
  int main(void)
  {
    HAL_Init();
  
    while (1)
    { 
      HAL_GPIO_TogglePin(LD2_GPIO_Port,LD2_Pin);
      sleep(1);  // this line throws a error, when compiling
    }
  }
  </code></pre>
  
  <p>the compiler gives me following error:</p>
  
  <pre><code>/usr/lib/gcc/arm-none-eabi/7.4.0/../../../../arm-none-eabi/bin/ld: CMakeFiles/untitled2.elf.dir/Src/main.c.obj: in function `main':
  /home/heinrich/CLionProjects/untitled2/Src/main.c:106: undefined reference to `sleep'
  collect2: error: ld returned 1 exit status
  make[3]: *** [CMakeFiles/untitled2.elf.dir/build.make:391: untitled2.elf] Fehler 1
  make[2]: *** [CMakeFiles/Makefile2:73: CMakeFiles/untitled2.elf.dir/all] Fehler 2
  make[1]: *** [CMakeFiles/Makefile2:85: CMakeFiles/untitled2.elf.dir/rule] Fehler 2
  make: *** [Makefile:118: untitled2.elf] Fehler 2
  </code></pre>
  
  <p>I think, the problem is a not-installed libary, but i installed everything in the fedora-repos for arm-gcc</p>
  
  <p>OS: Fedora 30
  IDE: CLion
  Toolchain: Arm-gcc-none-eabi</p>