Avoid recompiling postgres_ffi when there has been no changes (#12292)

Every time you run `make`, it runs `make install` on all the PostgreSQL
sources, which copies the header files. That in turn triggers a rebuild
of the `postgres_ffi` crate, and everything that depends on it. We had
worked around this earlier (see #2458), by passing a custom INSTALL
script to the Postgres makefiles, which refrains from updating the
modification timestamp on headers when they have not been changed, but
the v14 makefile didn't obey INSTALL for the header files. Backporting
c0a1d7621b to v14 fixes that.

This backports upstream PostgreSQL commit c0a1d7621b to v14.

Corresponding PR in the 'postgres' repo:
https://github.com/neondatabase/postgres/pull/660

.github/workflows/build-macos.yml

@@ -110,7 +110,7 @@ jobs:
 
   build-walproposer-lib:
     if: |
-      inputs.pg_versions != '[]' || inputs.rebuild_everything ||
+      contains(inputs.pg_versions, 'v17') || inputs.rebuild_everything ||
       contains(github.event.pull_request.labels.*.name, 'run-extra-build-macos')  ||
       contains(github.event.pull_request.labels.*.name, 'run-extra-build-*') ||
       github.ref_name == 'main'

vendor/revisions.json

@@ -13,6 +13,6 @@
   ],
   "v14": [
     "14.18",
-    "6770bc251301ef40c66f7ecb731741dc435b5051"
+    "9085654ee8022d5cc4ca719380a1dc53e5e3246f"
   ]
 }