Tests/RunCMake/CommandLine: Check tilde shell expansion more precisely

Revise the test from commit 01f92efeb0 (Restore expansion of leading '~'
as home directory in input paths, 2025-04-02, v4.0.1~12^2) to tolerate
`~` in the path to CMake's source or build tree.  If tilde `~` shell
expansion fails it can only occur at the beginning of a path component.