app-misc/tmux: enable sixel support

app-misc/tmux/files/tmux-2.4-flags.patch

@@ -0,0 +1,15 @@
+ Makefile.am |    3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+--- tmux-2.4/Makefile.am
++++ tmux-2.4/Makefile.am
+@@ -17,9 +17,8 @@
+ 
+ # Set flags for gcc.
+ if IS_GCC
+-AM_CFLAGS += -std=gnu99 -O2
++AM_CFLAGS += -std=gnu99
+ if IS_DEBUG
+-AM_CFLAGS += -g
+ AM_CFLAGS += -Wno-long-long -Wall -W -Wformat=2
+ AM_CFLAGS += -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
+ AM_CFLAGS += -Wwrite-strings -Wshadow -Wpointer-arith -Wsign-compare