[202012] [generate_dump] allow to extend dump with plugin scripts (#2269

)

- What I did
Added support for tech support extension scripts,
by cherry-picking of #1335 to 202012 branch.

The purpose is to have dumps of extensions in SONiC techsupport, even without App Extension infrastructure.
The new application will write a file that contains the dump command into /usr/bin/debug-dump folder, and it will appear in the output of show techsupport command.

- How I did it
It looks at /usr/bin/debug-dump for scripts, if it finds one it will execute them and save the output to dump/ folder.

- How to verify it
Write a simple scripts with an output and place it under /usr/bin/debug-dump/

scripts/generate_dump

@@ -32,6 +32,7 @@ DUMPDIR=/var/dump
 TARDIR=$DUMPDIR/$BASE
 TARFILE=$DUMPDIR/$BASE.tar
 LOGDIR=$DUMPDIR/$BASE/dump
+PLUGINS_DIR=/usr/local/bin/debug-dump
 NUM_ASICS=1
 HOME=${HOME:-/root}
 USER=${USER:-root}
@@ -1216,6 +1217,14 @@ main() {
     save_cmd "docker ps -a" "docker.ps"
     save_cmd "docker top pmon" "docker.pmon"
 
+    if [[ -d ${PLUGINS_DIR} ]]; then
+        local -r dump_plugins="$(find ${PLUGINS_DIR} -type f -executable)"
+        for plugin in $dump_plugins; do
+            # save stdout output of plugin and gzip it
+            save_cmd "$plugin" "$(basename $plugin)" true
+        done
+    fi
+
     save_saidump
 
     if [[ "$asic" = "mellanox" ]]; then