Here’s the relevant job. All other jobs triggered by the same commit succeeded. This kind of error happens sporadically in different places, and restarting the job in question resulted in a successful build. Relevant part of the logs:
[ 90%] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86PadShortFunction.cpp.o c++: internal compiler error: Killed (program cc1plus) Please submit a full bug report, with preprocessed source if appropriate. See <file:///usr/share/doc/gcc-5/README.Bugs> for instructions. lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/build.make:278: recipe for target 'lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86ISelDAGToDAG.cpp.o' failed make: *** [lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86ISelDAGToDAG.cpp.o] Error 4 make: *** Waiting for unfinished jobs....
Looking around for the specific C++ error seems to point to the process being killed due to out-of-memory. However, nothing in the test itself should be using too much memory, or else this failure would have been more consistent for this particular job and/or commit.
This example may be related. It has a segfault inside QEMU, while other QEMU-related jobs from the same trigger commit passed without issues.