'error: linker command failed' when running 'flang -v'

[BenWibking]

I've installed flang from the master branch via Spack:

spack install flang@master%gcc

but I get this (spurious?) error when I try to run flang without any arguments:

% flang
/usr/bin/ld: /home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/lib/libflangmain.a(flangmain.c.o): in function `main':
/tmp/benwibking/spack-stage/spack-stage-flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/spack-src/runtime/flangmain/flangmain.c:59: undefined reference to `MAIN_'
clang-7: error: linker command failed with exit code 1 (use -v to see invocation)

% flang -v
clang version 7.1.0 (https://github.com/flang-compiler/flang-driver.git 984936abdd04b40140c98ba5e273a3c006780612) (https://github.com/flang-compiler/llvm.git 939ad19087ec3c18718b2b6bb7ae40d7945f54d8)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/llvm-flang-release_70-h5odw56xr3vfitwgpbyxzwitrkdvwtju/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Candidate multilib: .;@m64
Selected multilib: .;@m64
Found CUDA installation: /usr/local/cuda, version unknown
 "/usr/bin/ld" --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o a.out /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/crt1.o /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/9/crtbegin.o -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/pgmath-master-zdwn62fc6sf54y6uwf75xjxkrpfcbxix/lib -L/usr/lib/gcc/x86_64-linux-gnu/9 -L/usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/9/../../../../lib64 -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib64 -L/usr/lib/x86_64-linux-gnu/../../lib64 -L/usr/lib/gcc/x86_64-linux-gnu/9/../../.. -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/llvm-flang-release_70-h5odw56xr3vfitwgpbyxzwitrkdvwtju/bin/../lib -L/lib -L/usr/lib -lflangmain -rpath /home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/lib -rpath /home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/pgmath-master-zdwn62fc6sf54y6uwf75xjxkrpfcbxix/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/pgmath-master-zdwn62fc6sf54y6uwf75xjxkrpfcbxix/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/llvm-flang-release_70-h5odw56xr3vfitwgpbyxzwitrkdvwtju/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/hwloc-2.2.0-7gcxkrsj2t7v5t7d5p2pi4qlniy2ibc7/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/libxml2-2.9.10-33ygryipzgrxjackfzgwh2iki6c7bjjc/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/zlib-1.2.11-2pwsgfxppopolmjj6tf34k5jsaqzpodo/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/xz-5.2.5-3xi5ln4dwblhkonbuvyb5tir44sxknkg/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/libiconv-1.16-dukcmslv5qzcajajpbldun56gxtdgkxp/lib -L/home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/libpciaccess-0.16-fei7nzugzy3ap7ndifbxwwyzltyilltb/lib -lflang -lflangrti -lpgmath -lompstub -lm -lrt -lpthread -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/9/crtend.o /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/crtn.o
/usr/bin/ld: /home/benwibking/spack/opt/spack/linux-ubuntu20.04-zen2/gcc-9.3.0/flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/lib/libflangmain.a(flangmain.c.o): in function `main':
/tmp/benwibking/spack-stage/spack-stage-flang-master-5fncumt7p65ya7gtpqzvbzkghbq5g3ma/spack-src/runtime/flangmain/flangmain.c:59: undefined reference to `MAIN_'
clang-7: error: linker command failed with exit code 1 (use -v to see invocation)