Comment 3 for bug 1867173

Here a backtrace in GDB, let me know if I can check anything for you there:

ubuntu@s1lp05:~/postgresql-12-12.2/build/tmp_install/usr/lib/postgresql/12/lib/bitcode$ gdb /usr/lib/llvm-10/bin/llvm-ltoGNU gdb (Ubuntu 9.1-0ubuntu1) 9.1
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Reading symbols from /usr/lib/llvm-10/bin/llvm-lto...
Reading symbols from /usr/lib/debug/.build-id/2c/dfd421eef6cbe0600d24e01b38e71763bb4333.debug...
(gdb) run -thinlto -thinlto-action=thinlink -o postgres.index.bc postgres/access/brin/brin.bc
Starting program: /usr/lib/llvm-10/bin/llvm-lto -thinlto -thinlto-action=thinlink -o postgres.index.bc postgres/access/brin/brin.bc
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/s390x-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
handleErrors<(lambda at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:988:33)>(void) ()
    at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:907
907 /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h: No such file or directory.
(gdb) bt
#0 handleErrors<(lambda at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:988:33)>(void) ()
    at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:907
#1 0x000003fff9d512e0 in handleAllErrors<(lambda at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:988:33)> ()
    at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:925
#2 toString () at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/include/llvm/Support/Error.h:988
#3 0x000003fffab16536 in addModule () at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/lib/LTO/ThinLTOCodeGenerator.cpp:515
#4 0x000000008001c5ce in thinLink () at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/tools/llvm-lto/llvm-lto.cpp:577
#5 0x000000008001464a in run () at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/tools/llvm-lto/llvm-lto.cpp:541
#6 main () at /build/llvm-toolchain-10-PvK6ID/llvm-toolchain-10-10.0.0~+rc3/llvm/tools/llvm-lto/llvm-lto.cpp:912