Shallow clones can't find submodule commits

[palmer-dabbelt]

I'm trying to build this, and I'm getting a bunch of failures along the lines of

$ make -j1
cd /scratch/work/20250224-large_fpic/riscv-gnu-toolchain/build/.. && \
flock `git rev-parse --git-dir`/config git submodule init /scratch/work/20250224-large_fpic/riscv-gnu-toolchain/build/../gcc/ && \
flock `git rev-parse --git-dir`/config git submodule update --progress --depth 1 /scratch/work/20250224-large_fpic/riscv-gnu-toolchain/build/../gcc/
Cloning into '/scratch/work/20250224-large_fpic/riscv-gnu-toolchain/gcc'...
remote: Enumerating objects: 146250, done.        
remote: Counting objects: 100% (146250/146250), done.        
remote: Compressing objects: 100% (112597/112597), done.        
Receiving objects: 100% (146250/146250), 175.64 MiB | 12.53 MiB/s, done.
remote: Total 146250 (delta 37683), reused 90982 (delta 31625), pack-reused 0        
Resolving deltas: 100% (37683/37683), done.
remote: Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
error: Server does not allow request for unadvertised object 04696df09633baf97cdbbdd6e9929b9d472161d3
fatal: Fetched in submodule path 'gcc', but it did not contain 04696df09633baf97cdbbdd6e9929b9d472161d3. Direct fetching of that commit failed.
fatal: 
make: *** [Makefile:348: /scratch/work/20250224-large_fpic/riscv-gnu-toolchain/build/../gcc/.git] Error 128

(I get similar results from just a git submodule update --init --recursive, and in binutils). As far as I can tell it's because the target servers don't support fetching by hash, and the shallow clones don't end up pulling in the submodule commits via a dependency.

[TommyMurphyTM1234]

Duplicate issue - see here:

• git submodule update fails #1669

Please use the workaround described here for now:

• git submodule update fails #1669 (comment)