ctest_update: Fix crash when handling svn externals
Refactoring in !799 (merged) switched cmCTestSVN::Repositories
from std::list
to
std::vector
. This can cause re-allocation when svn externals are
processed and break the RootInfo
pointer that is supposed to point at
the first repository element. Switch back to std::list
so that the
address remains stable.
Fixes: #17854 (closed)