fix(ci): give the Windows tests vcpkg's DLLs; skip root-only perm checks

- Windows: the first test executable died with STATUS_DLL_NOT_FOUND
  (0xc0000135) because vcpkg's x64-windows DLLs (ffmpeg and its codecs)
  were not on PATH; add vcpkg_installed/x64-windows/bin in the configure
  step.
- openKylin: failure_paths_report_cleanly asserts that a read-only library
  write fails, but the container runs as root, which bypasses the file
  permission bits (CAP_DAC_OVERRIDE) and the write succeeds; skip that
  sub-check when euid is 0 (read from /proc/self/status on Linux) and note
  it in the log.

.github/workflows/ci.yml

@@ -340,6 +340,10 @@ jobs:
           "FFMPEG_DIR=$prefix" >> $env:GITHUB_ENV
           "PKG_CONFIG_PATH=$prefix\lib\pkgconfig" >> $env:GITHUB_ENV
           "$prefix\tools\pkgconf" >> $env:GITHUB_PATH
+          # The test binaries link vcpkg's dynamic DLLs (ffmpeg and its
+          # codecs): without this the runner reports STATUS_DLL_NOT_FOUND
+          # when the first test executable starts.
+          "$prefix\bin" >> $env:GITHUB_PATH
           # Bundled OCIO: ocio-sys' vendored sources build with the MSVC
           # toolchain (what they need — the MSYS2 package was the
           # workaround, not the preference), so no OCIO_INSTALL_DIR and