cmake: declutter root + remove obsolete variables

cmake/cmake_uninstall.cmake.in

@@ -0,0 +1,17 @@
+if (NOT EXISTS "@CMAKE_BINARY_DIR@/install_manifest.txt")
+    message(FATAL_ERROR "Cannot find install manifest: \"@CMAKE_BINARY_DIR@/install_manifest.txt\"")
+endif()
+
+file(READ "@CMAKE_BINARY_DIR@/install_manifest.txt" files)
+string(REGEX REPLACE "\n" ";" files "${files}")
+foreach(file ${files})
+    message(STATUS "Uninstalling \"$ENV{DESTDIR}${file}\"")
+    execute_process(
+        COMMAND @CMAKE_COMMAND@ -E remove "$ENV{DESTDIR}${file}"
+        OUTPUT_VARIABLE rm_out
+        RESULT_VARIABLE rm_retval
+    )
+    if(NOT ${rm_retval} EQUAL 0)
+        message(FATAL_ERROR "Problem when removing \"$ENV{DESTDIR}${file}\"")
+    endif (NOT ${rm_retval} EQUAL 0)
+endforeach()