ci: add iOS platform

.github/workflows/ios.yml

@@ -0,0 +1,15 @@
+name: iOS
+
+on: [push, pull_request]
+
+jobs:
+  ios:
+    runs-on: macos-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: build
+      run: |
+        cmake -B build -G Xcode -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_DEPLOYMENT_TARGET=11.0 -DCMAKE_DISABLE_FIND_PACKAGE_OpenSSL=ON -DUSE_OPENSSL=OFF -DCMAKE_C_FLAGS="-DDARWIN -Werror"
+        cmake --build build -- CODE_SIGNING_ALLOWED=NO

src/md5/wrap.c

@@ -7,6 +7,8 @@
 #include <stddef.h>
 #include <openssl/evp.h>
 #include <openssl/md5.h>
+#elif defined (__APPLE__)
+#include <CommonCrypto/CommonDigest.h>
 #endif
 #include <re_types.h>
 #include <re_fmt.h>
@@ -31,6 +33,8 @@ void md5(const uint8_t *d, size_t n, uint8_t *md)
 	EVP_DigestUpdate(ctx, d, n);
 	EVP_DigestFinal_ex(ctx, md, NULL);
 	EVP_MD_CTX_free(ctx);
+#elif defined (__APPLE__)
+	CC_MD5(d, (unsigned int)n, md);
 #else
 #error missing MD5 backend
 #endif