meson: macos: Use -Wl,-undefined,error for modules

meson defaults to -Wl,-undefined,dynamic_lookup for modules, which we don't
want because a) it's different from what we do for autoconf, b) it causes
warnings starting in macOS Ventura.

Discussion: https://postgr.es/m/20221015211955.q4cwbsfkyk3c4ty3@awork3.anarazel.de

meson.build

@@ -228,6 +228,10 @@ elif host_system == 'darwin'
   message('darwin sysroot: @0@'.format(pg_sysroot))
   cflags += ['-isysroot', pg_sysroot]
   ldflags += ['-isysroot', pg_sysroot]
+  # meson defaults to -Wl,-undefined,dynamic_lookup for modules, which we
+  # don't want because a) it's different from what we do for autoconf, b) it
+  # causes warnings starting in macOS Ventura
+  ldflags_mod += ['-Wl,-undefined,error']
 
 elif host_system == 'freebsd'
   sema_kind = 'unnamed_posix'