reverted removal of CPACK_SOURCE_PACKAGE_FILE_NAME

The use of `CPACK_PACKAGE_NAME` leads to
`cppformat-<version>-Source.zip` as the name for the source package
which is different from the expected `cppformat-<version>.zip`.

CMakeLists.txt

@@ -156,6 +156,7 @@ if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.gitignore")
 
   set(CPACK_SOURCE_GENERATOR ZIP)
   set(CPACK_SOURCE_IGNORE_FILES ${ignored_files})
+  set(CPACK_SOURCE_PACKAGE_FILE_NAME "cppformat-${CPPFORMAT_VERSION}")
   set(CPACK_PACKAGE_NAME "cppformat")
   set(CPACK_RESOURCE_FILE_README ${FORMAT_SOURCE_DIR}/README.rst)
   include(CPack)