ci: run sha256 builds during our nightly runs

.github/workflows/nightly.yml

@@ -265,10 +265,40 @@ jobs:
             RUN_INVASIVE_TESTS: true
             SKIP_PROXY_TESTS: true
           os: ubuntu-latest
+
+        # Experimental: SHA256 support
+        - name: "Linux (SHA256, Xenial, Clang, OpenSSL)"
+          id: xenial-clang-openssl
+          container:
+            name: xenial
+          env:
+            CC: clang
+            CMAKE_GENERATOR: Ninja
+            CMAKE_OPTIONS: -DUSE_HTTPS=OpenSSL -DDEPRECATE_HARD=ON -DUSE_LEAK_CHECKER=valgrind -DUSE_GSSAPI=ON -DUSE_SSH=ON
+          os: ubuntu-latest
+        - name: "macOS (SHA256)"
+          id: macos
+          os: macos-10.15
+          env:
+            CC: clang
+            CMAKE_OPTIONS: -DREGEX_BACKEND=regcomp_l -DDEPRECATE_HARD=ON -DUSE_LEAK_CHECKER=leaks -DUSE_GSSAPI=ON -DEXPERIMENTAL_SHA256=ON
+            PKG_CONFIG_PATH: /usr/local/opt/openssl/lib/pkgconfig
+            SKIP_SSH_TESTS: true
+            SKIP_NEGOTIATE_TESTS: true
+          setup-script: osx
+        - name: "Windows (SHA256, amd64, Visual Studio)"
+          id: windows-amd64-vs
+          os: windows-2019
+          env:
+            ARCH: amd64
+            CMAKE_GENERATOR: Visual Studio 16 2019
+            CMAKE_OPTIONS: -A x64 -DWIN32_LEAKCHECK=ON -DDEPRECATE_HARD=ON -DEXPERIMENTAL_SHA256=ON
+            SKIP_SSH_TESTS: true
+            SKIP_NEGOTIATE_TESTS: true
       fail-fast: false
-    name: "Build ${{ matrix.platform.name }}"
     env: ${{ matrix.platform.env }}
     runs-on: ${{ matrix.platform.os }}
+    name: "Build ${{ matrix.platform.name }}"
     steps:
     - name: Check out repository
       uses: actions/checkout@v3