Since commit 3958ed87 (LCC: Add policy CMP0129 regarding interpreting
LCC as GNU, 2021-10-19, v3.23.0-rc1~508^2) we intended to enable policy
`CMP0129` in RunCMake tests via `-DCMAKE_POLICY_DEFAULT_CMP0129=NEW`.
Fix the condition activating that to check `CMAKE_C_COMPILER_ID` where
it is always available.

Remove now-unnecessary CMP0129 settings in RunCMake cases.