Experiment: build FFmpeg on Travis for Linux.

Let's see how workable / problematic this is.  Can improve our scripts
more to make this easier / more automatic.

Author: unknownbrackets

.travis.sh

@@ -114,6 +114,10 @@ travis_install() {
 travis_script() {
 	# Compile PPSSPP
 	if [ "$PPSSPP_BUILD_TYPE" = "Linux" ]; then
+		pushd ffmpeg
+		./linux_x86-64.sh
+		popd
+
 		if [ "$QT" = "TRUE" ]; then
 			./b.sh --qt
 		else

.travis.yml

@@ -19,6 +19,8 @@ addons:
       - lib32z1
       - lib32z1-dev
       - lib32bz2-1.0
+      - yasm
+      - diffutils
 
 cache:
   - apt