CMake: provide a log of what went wrong when not able to download a package.

Author: agarny

cmake/packages.cmake

@@ -198,7 +198,7 @@ function(retrieve_package PACKAGE_NAME PACKAGE_VERSION PACKAGE_REPOSITORY RELEAS
             set(PACKAGE_URL "https://github.com/agarny/${PACKAGE_REPOSITORY}/releases/download/707e211/${PACKAGE_FILE}")
         endif()
 
-        file(DOWNLOAD ${PACKAGE_URL} ${REAL_PACKAGE_FILE} STATUS STATUS)
+        file(DOWNLOAD ${PACKAGE_URL} ${REAL_PACKAGE_FILE} LOG LOG STATUS STATUS)
 
         # Uncompress the package, should we have managed to retrieve it.
 
@@ -234,7 +234,7 @@ function(retrieve_package PACKAGE_NAME PACKAGE_VERSION PACKAGE_REPOSITORY RELEAS
             file(REMOVE_RECURSE ${INSTALL_DIR})
 
             message(STATUS "Retrieving Package ${PACKAGE_NAME} - Failed")
-            message(FATAL_ERROR "The ${PACKAGE_NAME} package could not be retrieved from ${PACKAGE_URL}.")
+            message(FATAL_ERROR "The ${PACKAGE_NAME} package could not be retrieved from ${PACKAGE_URL}.\n${LOG}")
         endif()
     endif()