`./configure` mingw32ce builds enable C99 mode automatically, that
triggers compiler warnings in gcc 4.4.0. We initially worked it around
in CI by suppressing the detection of C99 with `ac_cv_prog_cc_c99=no`.
Replace it with automatically silencing the bogus warnings in C99 mode,
for all build systems:
```
lib/ftp.c: In function 'Curl_GetFTPResponse':
lib/ftp.c:726: error: format '%zd' expects type 'signed size_t', but argument 4 has type 'ssize_t'
lib/ws.c: In function 'ws_dec_pass_payload':
lib/ws.c:304: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t'
lib/ws.c: In function 'ws_enc_write_head':
lib/ws.c:581: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'long int'
lib/vtls/schannel.c: In function 'schannel_connect_step1':
lib/vtls/schannel.c:1122: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t'
lib/vtls/schannel.c: In function 'schannel_connect_step2':
lib/vtls/schannel.c:1311: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t'
lib/vtls/schannel.c: In function 'schannel_send':
lib/vtls/schannel.c:1793: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t'
lib/vtls/schannel.c:1810: error: format '%zd' expects type 'signed size_t', but argument 3 has type 'ssize_t'
lib/vtls/schannel.c: In function 'schannel_shutdown':
lib/vtls/schannel.c:2286: error: format '%zd' expects type 'signed size_t', but argument 4 has type 'ssize_t'
lib/vtls/vtls.c: In function 'ssl_cf_recv':
lib/vtls/vtls.c:1422: error: format '%zd' expects type 'signed size_t', but argument 5 has type 'ssize_t'
```
Ref: https://github.com/curl/curl/actions/runs/13533841306/job/37821720902?pr=16492#step:9:20
Also: simplify Windows CE job configuration in GHA/windows.
Follow-up to 2a292c3984#15975Closes#16492
3efc53f5e9