Just had a go w/ Xcode 13.3. Everything worked pretty well, I just had to bump the target spec and bitcode to make it work:
diff --git a/scripts/build.sh b/scripts/build.sh
index 31a2b47..25551ec 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -42,7 +42,7 @@ make clean
fi
if [ ! -d $BUILD_DIR/build/lib.catalyst ]; then
-./Configure --prefix="$BUILD_DIR/build" --openssldir="$BUILD_DIR/build/ssl" no-shared darwin64-$HOST_ARC-cc --target=$BUILD_ARC-apple-ios13.0-macabi -isysroot $MACSYSROOT/SDKs/MacOSX.sdk -I$MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/usr/include/ -isystem $MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/usr/include -iframework $MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/System/Library/Frameworks
+./Configure --prefix="$BUILD_DIR/build" --openssldir="$BUILD_DIR/build/ssl" no-shared darwin64-$HOST_ARC-cc --target=$BUILD_ARC-apple-ios13.4-macabi -isysroot $MACSYSROOT/SDKs/MacOSX.sdk -I$MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/usr/include/ -isystem $MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/usr/include -iframework $MACSYSROOT/SDKs/MacOSX.sdk/System/iOSSupport/System/Library/Frameworks
make clean
make -j$THREAD_COUNT
@@ -65,7 +65,7 @@ fi
if [ ! -d $BUILD_DIR/build/lib.ios ]; then
-./Configure --prefix="$BUILD_DIR/build" --openssldir="$BUILD_DIR/build/ssl" no-shared no-dso no-hw no-engine ios64-xcrun -fembed-bitcode-marker
+./Configure --prefix="$BUILD_DIR/build" --openssldir="$BUILD_DIR/build/ssl" no-shared no-dso no-hw no-engine ios64-xcrun -fembed-bitcode
make clean
make -j$THREAD_COUNT