CI: Fix build errors on Ubuntu 18.04.

libgit2-dev depends on libcurl4-gnutls-dev, CMake < 3.12 has no IMPORTED
target for libcurl.

.drone.yml

@@ -92,7 +92,7 @@ steps:
   - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
   - apt-get update -q
   - apt-get install -qq build-essential cmake clang pkg-config
-  - apt-get install -qq catch libcgicc-dev nlohmann-json-dev libgit2-dev libcurl4-openssl-dev
+  - apt-get install -qq catch libcgicc-dev nlohmann-json-dev libgit2-dev libcurl4-gnutls-dev
   - rm -rf build && mkdir -p build && cd build
   - cmake -G "Unix Makefiles" -DWITH_TESTS=YES ..
   - make VERBOSE=1

src/CMakeLists.txt

@@ -18,8 +18,13 @@ target_link_libraries(fediblock
   PkgConfig::cgicc
   nlohmann_json
   std::filesystem
-  PkgConfig::libgit2
-  CURL::libcurl)
+  PkgConfig::libgit2)
+
+if(${CMAKE_VERSION} VERSION_LESS 3.12)
+  target_link_libraries(fediblock PUBLIC ${CURL_LIBRARIES})
+else()
+  target_link_libraries(fediblock PUBLIC CURL::libcurl)
+endif()
 
 add_executable(${PROJECT_NAME} main.cpp)