install.sh: Fix bee registery of /etc/files

The function install_etc_files contains a bug which causes the files in
etc not to be probably registered in the crafted bee index of the
"mxtools-0.0-0" package.

The reason is, that the functions install_exe and install_data are
called from the last command of a pipeline. By default, this is executed
in a subshell, so the implicit modification of the global variable
INSTALLED_FILES is not seen by main process, which later uses it to
generate the index.

Use the "lastpipe" shell option, which makes the last command of a
pipeline run in the main shell process.

install.sh

@@ -103,6 +103,7 @@ function install_symlink()
 
 function install_etc_files()
 {
+    shopt -s lastpipe
     (cd etc ; find * -type f) | while read -r path; do
         if [[ -x etc/$path ]]; then
             install_exec etc/$path "$DESTDIR$sysconfdir/$path"