Utilities: Avoid OpenSSL version check under forks

When finding BoringSSL, LibreSSL, or AWS-LC, version information may be
unavailable. Amend commit 54686cae64 (Utilities: Require OpenSSL >=
3.0.0 at configure time, 2026-06-26) by using the checks from upstream
curl to only error if we're using OpenSSL proper.

Fixes: #27978

Source/Modules/CMakeBuildUtilities.cmake

@@ -153,7 +153,7 @@ else()
     set(CURL_CA_BUNDLE "" CACHE FILEPATH "Path to SSL CA Certificate Bundle")
     set(CURL_CA_PATH "" CACHE PATH "Path to SSL CA Certificate Directory")
     mark_as_advanced(CURL_CA_BUNDLE CURL_CA_PATH)
-    find_package(OpenSSL 3.0.0)
+    find_package(OpenSSL)
   endif()
   if(NOT CMAKE_USE_SYSTEM_NGHTTP2)
     # Tell curl's FindNGHTTP2 module to use our library.

Utilities/cmcurl/CMakeLists.txt

@@ -1011,7 +1011,7 @@ if(_use_core_foundation_and_core_services)
 endif()
 
 if(CURL_USE_OPENSSL)
-  find_package(OpenSSL 3.0.0)
+  find_package(OpenSSL)
   if(NOT OpenSSL_FOUND)
     message(FATAL_ERROR
       "Could not find OpenSSL. Install an OpenSSL development package or "
@@ -1042,6 +1042,17 @@ if(CURL_USE_OPENSSL)
   endif()
   cmake_pop_check_state()
 
+  if(NOT HAVE_BORINGSSL AND NOT HAVE_AWSLC AND NOT HAVE_LIBRESSL)
+    # Under forks of OpenSSL, we cannot guarantee that version information
+    # will be available.
+    if(OPENSSL_VERSION VERSION_LESS 3.0.0)
+      message(FATAL_ERROR
+        "Found OpenSSL version ${OPENSSL_VERSION}. When building CMake with "
+        "vendored curl, at least version 3.0.0 is required, or configure "
+        "CMake with -DCMAKE_USE_OPENSSL=OFF to build without OpenSSL.")
+    endif()
+  endif()
+
   # Optionally build with a specific CA cert bundle.
   if(CURL_CA_BUNDLE)
     add_definitions(-DCURL_CA_BUNDLE="${CURL_CA_BUNDLE}")