ci: Add 32-bit MinGW64 build

This commit also raises the TEST_ITERS for wine tasks to the default.
The overhead of wine is negligible, so we can certainly afford the same
number of iterations as for native Linux tests.

.cirrus.yml

@@ -246,18 +246,22 @@ task:
   << : *CAT_LOGS
 
 task:
-  name: "x86_64 (mingw32-w64): Windows (Debian stable, Wine)"
   << : *LINUX_CONTAINER
   env:
-    WRAPPER_CMD: wine64-stable
-    SECP256K1_TEST_ITERS: 16
-    HOST: x86_64-w64-mingw32
+    WRAPPER_CMD: wine
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
     EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
+  matrix:
+    - name: "x86_64 (mingw32-w64): Windows (Debian stable, Wine)"
+      env:
+        HOST: x86_64-w64-mingw32
+    - name: "i686 (mingw32-w64): Windows (Debian stable, Wine)"
+      env:
+        HOST: i686-w64-mingw32
   << : *MERGE_BASE
   test_script:
     - ./ci/cirrus.sh