ffmpeg: explicitly set the target OS for Solaris

Signed-off-by: Rafaël Carré <funman@videolan.org>
(cherry picked from commit 3227fba5f6d152fa86df625f2521148fe5efa892)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/ffmpeg/rules.mak

@@ -139,7 +139,7 @@ ifdef HAVE_SOLARIS
 ifeq ($(ARCH),x86_64)
 FFMPEGCONF += --cpu=core2
 endif
-FFMPEGCONF += --enable-pic
+FFMPEGCONF += --target-os=sunos --enable-pic
 endif
 
 # Build