title: IAR linker does not recognize .a library
body: <p>I am developing an application for ST's STM32F4-Discovery development kit with the ARM Cortex-M4F core. </p>
  
  <p>I am using FreeRTOS in my application, which is intended to use the board's microphone and loudspeaker output.</p>
  
  <p>I am trying to use ST's audio playback and record demo as an example for setting up the I2S interface for the mic. But I am having a real hard time with the PDM filter library of this example. This library is provided as a <code>.a</code> file and when I try to copy it into my project I get this message during linking:</p>
  
  <blockquote>
    <p>Fatal Error[Li004]: file
    "C:\Users\Daniel\Desktop\FreeRTOSV7.3.0\FreeRTOS\Demo\CORTEX_M4F_STM32F407ZG-SK\libPDMFilter_IAR.a"
    is not an object or archive file</p>
  </blockquote>
  
  <p>I tried messing with the linker options and saying to manually add this library. But with no results.
  Does anyone knows how to link a <code>.a</code> library in IAR?</p>