Work around bug in git 2.27.1
For these versions, "git submodule update --remote" will fail for any submodules that don't specify a branch in .gitmodules, and which are currently checked out on a remote tracking branch that tracks a remote other than "origin". For our pipelines, this means almost any submodule which has a CrossCompilationSupport branch which has not yet been merged.
Work around it by first doing "git submodule update" without "--remote", which will put all submodules into detacehd HEAD state.