bug#40887: No substitutes for libreoffice / vigra

[Leo Famulari]

ci.guix.gnu.org is having trouble building vigra (a dependency of
libreoffice) because the build times out after 1 hour of silence [0]:

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[ 94%] Linking CXX executable test_threadpool
cd /tmp/guix-build-vigra-1.11.1.drv-0/build/test/threadpool && 
/gnu/store/iz9500ssxcqlyr74hg1jq10ycrh42yq1-cmake-minimal-3.15.1/bin/cmake -E 
cmake_link_script CMakeFiles/test_threadpool.dir/link.txt --verbose=1
/gnu/store/x3jx25cd3q363mr7nbgzrhrv1vza6cf7-gcc-7.4.0/bin/c++  -std=c++11 
-pthread 
-I/gnu/store/mh501jvl3hl2fja4n1iial5zjy36qrys-ilmbase-2.4.1/include/OpenEXR 
-ffloat-store -O2 -g -DNDEBUG  -rdynamic 
CMakeFiles/test_threadpool.dir/test.cxx.o 
CMakeFiles/test_threadpool.dir/testsuccess.cxx.o  -o test_threadpool 
Running test_threadpool
cd /tmp/guix-build-vigra-1.11.1.drv-0/build/test/threadpool && 
./run_test_threadpool.sh
building of `/gnu/store/mfnzxkhj4hiayk9lbb7vp5qxa9qjm1li-vigra-1.11.1.drv' 
timed out after 3600 seconds of silence
@ build-failed /gnu/store/mfnzxkhj4hiayk9lbb7vp5qxa9qjm1li-vigra-1.11.1.drv - 
timeout
------

It takes a lot of resources to build this package and people are
reporting difficulties on the mailing lists and IRC [1]. Is there anything
we can do to make it more likely to build on the CI servers?

[0] https://ci.guix.gnu.org/build/2613103/details
[1] https://bugs.gnu.org/40789
http://logs.guix.gnu.org/guix/2020-04-27.log#002722