oauth: Correct SSL dependency for libpq-oauth.a

libpq-oauth.a includes libpq-int.h, which includes OpenSSL headers. The
Autoconf side picks up the necessary include directories via CPPFLAGS,
but Meson needs the dependency to be made explicit.

Reported-by: Nathan Bossart <nathandbossart@gmail.com>
Tested-by: Nathan Bossart <nathandbossart@gmail.com>
Tested-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/aBTgjDfrdOZmaPgv%40nathan

src/interfaces/libpq-oauth/meson.build

@@ -25,7 +25,11 @@ libpq_oauth_st = static_library('libpq-oauth',
   libpq_oauth_sources,
   include_directories: [libpq_oauth_inc, postgres_inc],
   c_pch: pch_postgres_fe_h,
-  dependencies: [frontend_stlib_code, libpq_oauth_deps],
+  dependencies: [
+    frontend_stlib_code,
+    libpq_oauth_deps,
+    ssl, # libpq-int.h includes OpenSSL headers
+  ],
   kwargs: default_lib_args,
 )