find_package: Fix regression on `<PackageName>_ROOT` relative to CWD
In commit 9d44a77454 (find_*: Explicitly normalize found paths as they
exist on disk, 2024-10-17, v4.0.0-rc1~597^2~1), we removed path
normalization from the internal `cmSearchPath::AddPathInternal` helper.
Most call sites were updated to normalize input paths first, but search
paths derived from `<PackageName>_ROOT` CMake variables are no longer
normalized. Instead we normalize the path to the file found after
searching.
When `find_package` "config" mode considers a candidate CMake package
configuration file, normalize its path before loading the adjacent
package version file so that the latter is loaded by absolute path.
Otherwise `cmMakefile::ReadDependentFile` interprets a relative path
with respect to the current source directory rather than the current
working directory.
Fixes: #27279
4 files changed
