GHA: use more Ninja

Use it for AmigaOS, Android, dl-mingw 7.3.0 and 6.4.0 Windows builds.

Also drop explicit ninja installs.

dl-mingw:
Before:
7.3.0: https://github.com/curl/curl/actions/runs/14617346216/job/41008536465
6.4.0: https://github.com/curl/curl/actions/runs/14617346216/job/41008540878
After:
7.3.0: https://github.com/curl/curl/actions/runs/14617983032/job/41010584040?pr=17153
6.4.0: https://github.com/curl/curl/actions/runs/14617983032/job/41010586490?pr=17153

Follow-up to a366552243 #17115
Ref: https://github.com/actions/runner-images/issues/11391

Closes #17153

.github/workflows/windows.yml

@@ -467,7 +467,7 @@ jobs:
           for _chkprefill in '' ${{ matrix.chkprefill }}; do
             options=''
             [ "${_chkprefill}" = '_chkprefill' ] && options+=' -D_CURL_PREFILL=OFF'
-            cmake -B "bld${_chkprefill}" -G "${{ contains(matrix.url, '/winlibs_mingw/') && 'Ninja' || 'MSYS Makefiles' }}" ${options} \
+            cmake -B "bld${_chkprefill}" -G Ninja ${options} \
               -DCMAKE_C_COMPILER=gcc \
               -DCMAKE_BUILD_TYPE='${{ matrix.type }}' \
               -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_BATCH_SIZE=30 -DCURL_TEST_BUNDLES=ON \
@@ -562,7 +562,6 @@ jobs:
         timeout-minutes: 5
         run: |
           sudo apt-get -o Dpkg::Use-Pty=0 install mingw-w64 \
-            ${{ matrix.build == 'cmake' && 'ninja-build' || '' }} \
             ${{ matrix.compiler == 'clang-tidy' && 'clang' || '' }}
 
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4