Fixed mingw compilation.

It should be possible to simplify it with something like
find_library(CURL_LIBRARIES NAMES libcurl libcurldll PATHS "${PROJECT_SOURCE_DIR}/dependencies/lib")
so you can look if it works on Visual Studio.

And as far as I see pkgconfig is used only on unix. Btw. I'm also not sure if it should be if(UNIX AND NOT APPLE) ?

CMakeLists.txt

@@ -145,10 +145,10 @@ else()
 endif()
 
 if(BUILD_RECORDER)
-    include(FindPkgConfig)
     find_library(TURBOJPEG_LIBRARY NAMES turbojpeg libturbojpeg PATHS "${PROJECT_SOURCE_DIR}/dependencies/lib")
     mark_as_advanced(TURBOJPEG_LIBRARY)
     if(UNIX)
+        include(FindPkgConfig)
         pkg_check_modules(VPX vpx)
     else()
         find_path(VPX_INCLUDEDIR NAMES vpx/vpx_codec.h PATHS "${PROJECT_SOURCE_DIR}/dependencies/include")
@@ -401,8 +401,10 @@ else()
 endif()
 
 # CURL
-if(WIN32)
+if(MSVC)
     target_link_libraries(supertuxkart ${PROJECT_SOURCE_DIR}/dependencies/lib/libcurl.lib)
+elseif(MINGW)
+    target_link_libraries(supertuxkart ${PROJECT_SOURCE_DIR}/dependencies/lib/libcurldll.a)
 else()
     find_package(CURL REQUIRED)
     include_directories(${CURL_INCLUDE_DIRS})