ParseImplicitIncludeInfo: Canonicalize implicit include dirs
The implicit include directory extraction added by commit 5990ecb741
(Compute implicit include directories from compiler output, 2018-12-07,
v3.14.0-rc1~108^2) leaves paths like `/usr/lib/../include` unchanged.
Fix the logic to canonicalize such paths (e.g. to `/usr/include`)
as we do for implicit link directories already. This is important
to ensure the set of implicit directories is represented in the same
form as the include directories that will be compared to them.
Issue: #19095
17 files changed
