ExternalProject UPDATE_DISCONNECTED does not work empty update steps
The code
cmake_minimum_required(VERSION 3.2)
project(Armadillo-download NONE)
include(ExternalProject)
ExternalProject_Add(Armadillo-download
URL http://sourceforge.net/projects/arma/files/armadillo-6.700.3.tar.gz
URL_MD5 fac5aa395fcb5b9e52791f041827d872
TIMEOUT 180
UPDATE_DISCONNECTED 1
SOURCE_DIR "Armadillo-src"
BINARY_DIR "Armadillo-build"
CONFIGURE_COMMAND ""
BUILD_COMMAND ""
INSTALL_COMMAND ""
TEST_COMMAND ""
)
results in a build failure:
make[2]: *** No rule to make target `Armadillo-download-prefix/src/Armadillo-download-stamp/Armadillo-download-skip-update', needed by `Armadillo-download-prefix/src/Armadillo-download-stamp/Armadillo-download-configure'. Stop.
This was originally reported in discussion of #15904 (closed) but is a different issue than that one.