ffmpeg: fix path to /tmp

packages/ffmpeg/build.sh

@@ -3,7 +3,7 @@ TERMUX_PKG_DESCRIPTION="Tools and libraries to manipulate a wide range of multim
 TERMUX_PKG_LICENSE="GPL-3.0"
 # NOTE: mpv has to be rebuilt and version bumped after updating ffmpeg.
 TERMUX_PKG_VERSION=4.1.1
-TERMUX_PKG_REVISION=1
+TERMUX_PKG_REVISION=2
 TERMUX_PKG_SHA256=373749824dfd334d84e55dff406729edfd1606575ee44dd485d97d45ea4d2d86
 TERMUX_PKG_SRCURL=https://www.ffmpeg.org/releases/ffmpeg-${TERMUX_PKG_VERSION}.tar.xz
 # libbz2 is used by matroska decoder:

packages/ffmpeg/libavutil-file_open.c.patch

@@ -0,0 +1,21 @@
+diff -uNr ffmpeg-4.1.1/libavutil/file_open.c ffmpeg-4.1.1.mod/libavutil/file_open.c
+--- ffmpeg-4.1.1/libavutil/file_open.c	2019-02-09 22:56:02.000000000 +0200
++++ ffmpeg-4.1.1.mod/libavutil/file_open.c	2019-03-02 01:54:58.775236751 +0200
+@@ -119,7 +119,7 @@
+ #undef free
+     free(ptr);
+ #else
+-    size_t len = strlen(prefix) + 12; /* room for "/tmp/" and "XXXXXX\0" */
++    size_t len = strlen(prefix) + strlen("@TERMUX_PREFIX@/tmp/") + 7; /* room for "@TERMUX_PREFIX@/tmp/" and "XXXXXX\0" */
+     *filename  = av_malloc(len);
+ #endif
+     /* -----common section-----*/
+@@ -136,7 +136,7 @@
+ #   endif
+     fd = open(*filename, O_RDWR | O_BINARY | O_CREAT | O_EXCL, 0600);
+ #else
+-    snprintf(*filename, len, "/tmp/%sXXXXXX", prefix);
++    snprintf(*filename, len, "@TERMUX_PREFIX@/tmp/%sXXXXXX", prefix);
+     fd = mkstemp(*filename);
+ #if defined(_WIN32) || defined (__ANDROID__)
+     if (fd < 0) {