libusb (circleci).

circle.yml

@@ -1,6 +1,6 @@
 dependencies:
   pre:
-    - cd /tmp; git clone git://git.osmocom.org/rtl-sdr.git; cd rtl-sdr; mkdir build; cd build; cmake ../; make; sudo make install; sudo ldconfig
+    - sudo apt-get update; sudo apt-get install libusb-dev; cd /tmp; git clone git://git.osmocom.org/rtl-sdr.git; cd rtl-sdr; mkdir build; cd build; cmake ../; make; sudo make install; sudo ldconfig
   override:
     - make
 test: