pgsql: Add missing dependency of pg_dumpall to WIN32RES.

Add missing dependency of pg_dumpall to WIN32RES.

When cross-building to windows, or building with mingw on windows, the build
could fail with
x86_64-w64-mingw32-gcc: error: win32ver.o: No such file or director
because pg_dumpall didn't depend on WIN32RES, but it's recipe references
it. The build nevertheless succeeded most of the time, due to
pg_dump/pg_restore having the required dependency, causing win32ver.o to be
built.

Reported-By: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Discussion: https://postgr.es/m/CA+hUKGJeekpUPWW6yCVdf9=oBAcCp86RrBivo4Y4cwazAzGPng@mail.gmail.com
Backpatch: 10-, omission present on all live branches

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/097786fbbb58897fec12ed9bfff3940c77b5867b

Modified Files
--------------
src/bin/pg_dump/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)