common : use cpp-httplib as a cURL alternative for downloads

The existing cURL implementation is intentionally left untouched to
prevent any regressions and to allow for safe, side-by-side testing by
toggling the `LLAMA_CURL` CMake option.

Signed-off-by: Adrien Gallouët <[email protected]>

Author: angt

common/CMakeLists.txt

@@ -87,7 +87,20 @@ if (LLAMA_CURL)
     target_compile_definitions(${TARGET} PUBLIC LLAMA_USE_CURL)
     include_directories(${CURL_INCLUDE_DIRS})
     set(LLAMA_COMMON_EXTRA_LIBS ${LLAMA_COMMON_EXTRA_LIBS} ${CURL_LIBRARIES})
-endif ()
+else()
+    find_package(OpenSSL)
+    if (OpenSSL_FOUND)
+        message(STATUS "OpenSSL found: ${OPENSSL_VERSION}")
+        target_compile_definitions(${TARGET} PUBLIC CPPHTTPLIB_OPENSSL_SUPPORT)
+        target_link_libraries(${TARGET} PUBLIC OpenSSL::SSL OpenSSL::Crypto)
+        if (APPLE)
+            target_compile_definitions(${TARGET} PUBLIC CPPHTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN)
+            target_link_libraries(${TARGET} PUBLIC "-framework Security")
+        endif()
+    else()
+        message(STATUS "OpenSSL not found, SSL support disabled")
+    endif()
+endif()
 
 if (LLAMA_LLGUIDANCE)
     include(ExternalProject)