plugins repo: MEMLEAK

[daywalker90]

Our nightly CI in the plugins repo is failing on every(?) plugin because of a test teardown error containing a MEMLEAK:

 lightningd-1  **BROKEN** lightningd: MEMLEAK: 0x55c6b45ea3f8
 lightningd-1  **BROKEN** lightningd:   label=char[]
 lightningd-1  **BROKEN** lightningd:   alloc:
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:488 (tal_alloc_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:517 (tal_alloc_arr_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/path/path.c:211 (path_canon)
 lightningd-1  **BROKEN** lightningd:     lightningd/subd.c:1001 (find_my_abspath)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:515 (find_my_directory)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:536 (find_subdaemons_and_plugins)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:1196 (main)
 lightningd-1  **BROKEN** lightningd:   steal:
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:559 (tal_steal_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:856 (tal_dup_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/str/str.c:25 (tal_strndup_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/path/path.c:504 (path_dirname)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:530 (find_my_directory)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:536 (find_subdaemons_and_plugins)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:1196 (main)
 lightningd-1  **BROKEN** lightningd:   parents:
 lightningd-1  **BROKEN** lightningd: MEMLEAK: 0x55c6b45ea628
 lightningd-1  **BROKEN** lightningd:   label=char[]
 lightningd-1  **BROKEN** lightningd:   alloc:
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:488 (tal_alloc_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/tal.c:517 (tal_alloc_arr_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/str/str.c:81 (tal_vfmt_)
 lightningd-1  **BROKEN** lightningd:     ccan/ccan/tal/str/str.c:37 (tal_fmt_)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:557 (find_subdaemons_and_plugins)
 lightningd-1  **BROKEN** lightningd:     lightningd/lightningd.c:1196 (main)
 lightningd-1  **BROKEN** lightningd:   parents:
 lightningd-1  **BROKEN** lightningd:     struct plugins

This started 5 days ago on 48258ec and is still happening (ignore CI runs being green, we made them only error if the result changes from passing to error). First run showing these errors: https://github.com/lightningd/plugins/actions/runs/10295074709

[rustyrussell]

Ah, a minor leak which only happens when running an installed binary (not a local one). Thanks!

[daywalker90]

We are still leaking on 9a6325c:

**BROKEN** lightningd: MEMLEAK: 0x55ff8e8ec268
**BROKEN** lightningd:   label=char[]
**BROKEN** lightningd:   alloc:
**BROKEN** lightningd:     ccan/ccan/tal/tal.c:488 (tal_alloc_)
**BROKEN** lightningd:     ccan/ccan/tal/tal.c:517 (tal_alloc_arr_)
**BROKEN** lightningd:     ccan/ccan/tal/str/str.c:81 (tal_vfmt_)
**BROKEN** lightningd:     ccan/ccan/tal/str/str.c:37 (tal_fmt_)
**BROKEN** lightningd:     lightningd/lightningd.c:557 (find_subdaemons_and_plugins)
**BROKEN** lightningd:     lightningd/lightningd.c:1196 (main)
**BROKEN** lightningd:   parents:
**BROKEN** lightningd:     struct plugins

https://github.com/lightningd/plugins/actions/runs/10413820630