Remove unnecessary escape from include.sh

The older bash version of macOS does not understand this escape
and actually creates directories with "\" in their name. After this
change it actually works with both versions.

include.sh

@@ -11,7 +11,7 @@ do
     name="$(basename "$dir")"
     if [ "${name:0:1}" != "_" ]
     then
-        header="$include/${name/_/\/}.h"
+        header="$include/${name/_//}.h"
         pushd "$dir"
         cargo run --release --manifest-path "$cbindgen/Cargo.toml" -- \
             -c cbindgen.toml -o "$header" mod.rs