Catch2 failing to build on Windows

I meant to create this from a BFG (linked in comments) but that's broken right now.

The problem signature is:

[2022/10/16 23:12:54.489]   git checkout -b <new-branch-name>

[2022/10/16 23:12:54.489] HEAD is now at 216713a4 v2.13.8

[2022/10/16 23:12:54.489]       0 [main] sh (2388) C:\Program Files\Git\usr\bin\sh.exe: *** fatal error - cygheap base mismatch detected - 0xEF6410/0xFB6410.

I think this might be a tooling issue - the error seems to originate in the git shell running on cygwin than in catch2 or the cmake build scripts. Might be one for the build team.