build: Remove Mock ICD JSON file from install target

The mock ICD shouldn't be installed or be part of packages
that use the "make install" target to create packages.
The mock ICD shared lib wasn't added, but the JSON was.
diff --git a/icd/CMakeLists.txt b/icd/CMakeLists.txt
index 6216268..ae624a9 100644
--- a/icd/CMakeLists.txt
+++ b/icd/CMakeLists.txt
@@ -70,23 +70,6 @@
-# Add targets for JSON file install on Linux.
-# Need to remove the "./" from the library path before installing to /etc.
-        foreach (config_file ${ICD_JSON_FILES})
-            add_custom_target(${config_file}-staging-json ALL
-                COMMAND mkdir -p ${CMAKE_CURRENT_BINARY_DIR}/staging-json
-                COMMAND cp ${CMAKE_CURRENT_SOURCE_DIR}/${config_file}.json ${CMAKE_CURRENT_BINARY_DIR}/staging-json
-                COMMAND sed -i -e "/\"library_path\":/s$./libVkICD$libVkICD$" ${CMAKE_CURRENT_BINARY_DIR}/staging-json/${config_file}.json
-                VERBATIM
-                DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${config_file}.json
-                )
-            install(FILES ${CMAKE_CURRENT_BINARY_DIR}/staging-json/${config_file}.json DESTINATION ${CMAKE_INSTALL_SYSCONFDIR}/vulkan/icd.d)
-        endforeach(config_file)
-    endif()
 if (WIN32)
     macro(add_vk_icd target)