Build project from ExternalProject_Add using dockcross - cmake

Question

I am trying to build tinyxml2 using ExternalProject_Add. It works fine on my main system (Arch Linux), but I have some issues when running it inside dockcross (more specifically, dockcross/linux-armv6).
The following minimal CMakeLists.txt works (configure and build) from dockcross:
cmake_minimum_required(VERSION 3.1)
project(external-tinyxml2)
include(ExternalProject)
ExternalProject_add(
tinyxml2
URL https://github.com/leethomason/tinyxml2/archive/7.0.1.tar.gz
PREFIX tinyxml2
)
But the following doesn't (note the added line: CONFIGURE_COMMAND ${CMAKE_COMMAND} -S<SOURCE_DIR>):
cmake_minimum_required(VERSION 3.1)
project(external-tinyxml2)
include(ExternalProject)
ExternalProject_add(
tinyxml2
URL https://github.com/leethomason/tinyxml2/archive/7.0.1.tar.gz
PREFIX tinyxml2
CONFIGURE_COMMAND ${CMAKE_COMMAND} -S<SOURCE_DIR>
)
It actually results in the following error output:
[ 25%] No patch step for 'tinyxml2'
[ 37%] No update step for 'tinyxml2'
[ 50%] Performing configure step for 'tinyxml2'
CMake Deprecation Warning at CMakeLists.txt:11 (cmake_policy):
The OLD behavior for policy CMP0063 will be removed from a future version
of CMake.
The cmake-policies(7) manual explains that the OLD behaviors of all
policies are deprecated and that a policy should be set to OLD only under
specific short-term circumstances. Projects should be ported to the NEW
behavior and not rely on setting a policy to OLD.
CMake Error at /usr/share/cmake-3.13/Modules/CMakeDetermineCompilerId.cmake:161 (file):
file problem creating directory: /CMakeFiles/3.13.2/CompilerIdC
Call Stack (most recent call first):
/usr/share/cmake-3.13/Modules/CMakeDetermineCompilerId.cmake:31 (CMAKE_DETERMINE_COMPILER_ID_BUILD)
/usr/share/cmake-3.13/Modules/CMakeDetermineCCompiler.cmake:112 (CMAKE_DETERMINE_COMPILER_ID)
CMakeLists.txt:14 (project)
[... other similar errors ...]
CMake Error at /usr/share/cmake-3.13/Modules/CMakeTestCCompiler.cmake:37 (try_compile):
Failed to set working directory to /CMakeFiles/CMakeTmp/testCCompiler.c :
No such file or directory
Call Stack (most recent call first):
CMakeLists.txt:14 (project)
-- Configuring incomplete, errors occurred!
CMake Error: Cannot open file for write: /CMakeCache.txt.tmp
CMake Error: : System Error: Permission denied
CMake Error: Unable to open cache file for save. /CMakeCache.txt
CMake Error: : System Error: Permission denied
CMakeFiles/tinyxml2.dir/build.make:108: recipe for target 'tinyxml2/src/tinyxml2-stamp/tinyxml2-configure' failed
make[2]: *** [tinyxml2/src/tinyxml2-stamp/tinyxml2-configure] Error 1
make[2]: Leaving directory '/work/build'
CMakeFiles/Makefile2:72: recipe for target 'CMakeFiles/tinyxml2.dir/all' failed
make[1]: *** [CMakeFiles/tinyxml2.dir/all] Error 2
make[1]: Leaving directory '/work/build'
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
make: Leaving directory '/work/build
Building tinyxml2 directly from dockcross (i.e. without using ExternalProject_Add) works well.
What could be going wrong there?

Answer 1

That is actually a bug in CMake, as reported (and fixed) here.
The workaround, for CMake versions that have the bug, is to run it like so (note that -S<SOURCE_DIR> becomes <SOURCE_DIR>):
ExternalProject_add(
tinyxml2
URL https://github.com/leethomason/tinyxml2/archive/7.0.1.tar.gz
PREFIX tinyxml2
CONFIGURE_COMMAND ${CMAKE_COMMAND} <SOURCE_DIR>
)