build: target libtor.a only + add autotools to Windows msys2 install

Run #468 (the re-trigger after #467's fixes) failed with two more issues:

  1. Linux build-libtor step needed static OpenSSL libs (libssl.a,
     libcrypto.a) for the helper tools (tor-resolve, tor-print-ed-signing-cert)
     that the script was building by default. Ubuntu's libssl-dev
     package only ships the shared .so libs, not the static .a ones.
     We don't actually need the helper tools — Triangles only consumes
     libtor.a. Changed 'make' to 'make libtor.a' in build-libtor.sh
     so only the static library is built.

  2. Windows msys2 was missing autotools (aclocal, autoconf, automake,
     libtool). autogen.sh failed with 'aclocal: command not found'.
     Added 'mingw-w64-x86_64-autotools' and 'mingw-w64-x86_64-libtool'
     to the msys2 install lists in both Windows jobs.

If this one fails I'll show you the log. (Run #469 will be the test.)

.github/workflows/build-all.yml

@@ -161,6 +161,8 @@ jobs:
             mingw-w64-x86_64-miniupnpc
             mingw-w64-x86_64-zlib
             mingw-w64-x86_64-rocksdb
+            mingw-w64-x86_64-autotools
+            mingw-w64-x86_64-libtool
 
       - name: Set VERSION
         run: |