amp: patch termbox-sys for now to fix build

termbox-sys, which is an indirect dependency of amp, builds its
own termbox using waf, but forgets about libdir, which results
in the library being installed in a different location and the
build won't find it. Fix it here until upstream makes a release.

srcpkgs/amp/patches/termbox-fix.patch

@@ -0,0 +1,10 @@
+Status: submitted upstream https://github.com/gchp/termbox-sys/pull/20
+--- Cargo.toml
++++ Cargo.toml
+@@ -43,3 +43,6 @@ bench = []
+ name = "draw_buffer"
+ path = "benches/view/draw_buffer.rs"
+ harness = false
++
++[patch.crates-io]
++termbox-sys = { git = 'https://github.com/q66/termbox-sys' }