Build error with gcc11

[ametzler]

Hello,

this is https://bugs.debian.org/984213

vigra's testsuite does not run successfully with gcc11:

[ 71%] Linking CXX executable test_utilities
cd /<<PKGBUILDDIR>>/obj.x86_64-linux-gnu/test/utilities && /usr/bin/cmake -E cmake_link_script CMakeFiles/test_utilities.dir/link.txt --verbose=1
/usr/bin/c++ -std=c++11 -pthread -g -O2 -ffile-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -Wall -pipe -Wdate-time -D_FORTIFY_SOURCE=2 -Wl,-z,relro -Wl,-z,now -Wl,--as-needed -rdynamic CMakeFiles/test_utilities.dir/test.cxx.o CMakeFiles/test_utilities.dir/testsuccess.cxx.o -o test_utilities  -Wl,-rpath,/<<PKGBUILDDIR>>/obj.x86_64-linux-gnu/src/impex:/usr/lib/x86_64-linux-gnu/hdf5/serial ../../src/impex/libvigraimpex.so.11.1.11.1 -ljpeg -lpng -lz -ltiff -lIlmImf -lImath -lHalf -lIex -lIlmThread /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5.so /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5_hl.so -lsz -lz -ltiff -lIlmImf -lImath -lHalf -lIex -lIlmThread /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5.so /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5_hl.so -lsz 
Running test_utilities
cd /<<PKGBUILDDIR>>/obj.x86_64-linux-gnu/test/utilities && ./run_test_utilities.sh
Entering test suite UtilitiesTestSuite

Failure in AnyTest::test()
Unexpected signal: memory access violation
   (occured after line 1505 in file './test/utilities/test.cxx')

Fatal error - aborting test suite UtilitiesTestSuite.

Full build log can be found on http://people.debian.org/~doko/logs/20210228/filtered/gcc11/libvigraimpex_1.11.1+dfsg-8_unstable_gcc11.log