Depend on OIS on Linux only.

debian/control

@@ -28,7 +28,7 @@ Build-Depends: debhelper (>= 9),
                libv4l-dev,
                libusb-dev,
                libfreenect-dev,
-               libois-dev
+               libois-dev [linux-any]
 Standards-Version: 3.9.4
 Vcs-Browser: https://github.com/thomas-moulard/visp-deb
 Vcs-Git: git://github.com/thomas-moulard/visp-deb.git
@@ -55,7 +55,7 @@ Depends: libopencv-dev,
          libv4l-dev,
          libusb-dev,
          libfreenect-dev,
-         libois-dev,
+         libois-dev [linux-any],
          libvisp2 (= ${binary:Version}),
          ${misc:Depends}
 Suggests: libvisp-doc