[C++][CMake] Fix install/export targets and Windows runtime handling

[tanmoyPaul12]

Fixes #810

Reason for this PR

The current CMake installation logic in GraphAr does not reliably support
library distribution and downstream consumption, especially on Windows.

This PR addresses the CMake install and export issues discussed in #810
and makes runtime installation behavior consistent across platforms.

What changes are included in this PR?

• Remove duplicate and conflicting install logic for the graphar target
• Define a single canonical install(TARGETS graphar ...) rule
• Ensure headers and CMake package config files are installed correctly
• Fix Windows runtime (DLL) installation issues during cmake --install
• Validate installation with MSVC + vcpkg + Apache Arrow

Are these changes tested?

• Windows 11
• MSVC (Visual Studio 2026)
• CMake + vcpkg
• Apache Arrow installed via vcpkg (arrow[dataset,parquet])
• Verified:
  • cmake --build . --config Release
  • cmake --install . --config Release
  • Generated headers and CMake config files

Are there any user-facing changes?

No. This change affects CMake install and packaging behavior only and does not
modify GraphAr APIs or runtime behavior.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.18%. Comparing base (bac3630) to head (0d11cb8).
⚠️ Report is 77 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #819      +/-   ##
============================================
+ Coverage     77.17%   77.18%   +0.01%     
  Complexity      607      607              
============================================
  Files            84       85       +1     
  Lines          8854     8858       +4     
  Branches       1043     1043              
============================================
+ Hits           6833     6837       +4     
  Misses         1781     1781              
  Partials        240      240              

Flag	Coverage Δ
cpp	71.52% <ø> (ø)

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[yangxk1]

Hi @tanmoyPaul12 Thanks for the update! This PR improves the installation paths (especially for Windows), but it doesn't fully resolve #810 yet.

To fully support find_package(GraphAr) and the requested distribution goals, we still need:

1. The install(EXPORT ...) command to actually generate and install the CMake target files.
2. The RPATH configuration (e.g., $ORIGIN) and the hybrid linking strategy mentioned in the issue discussion.

Could you please address these points?

[tanmoyPaul12]

@yangxk1 I’ll update this PR to:

• Ensure install(EXPORT ...) generates usable CMake target files
• Address the RPATH ($ORIGIN) and hybrid linking strategy discussed in the issue

Thanks for the clarification — I’ll follow up with the changes shortly.

[keksmd]

@tanmoyPaul12 thanks for chasing #810 — reliable install/export is a real gap, and the MSVC + vcpkg validation you did is exactly the kind of testing this area was missing.

Unfortunately I think this PR has been overtaken by main and needs a rebase before it can be reviewed on its merits. GitHub currently reports it as CONFLICTING / DIRTY.

What changed underneath it

refactor(build): restructure CMake files into subdirectories (#877) (commit d1fe7f9) split cpp/CMakeLists.txt apart. The build_graphar() / build_graphar_with_arrow_bundled() macros and the install_graphar_target() helper that this PR edits no longer exist in cpp/CMakeLists.txt. The library and its install rule moved to cpp/src/CMakeLists.txt, which on current main reads:

install(TARGETS graphar graphar_thirdparty
        EXPORT graphar-targets
        ARCHIVE DESTINATION lib
        LIBRARY DESTINATION lib
        RUNTIME DESTINATION bin
        INCLUDES
        DESTINATION include)

So the three headline items of this PR — removing the duplicate/conflicting install logic, defining a single canonical install(TARGETS graphar ...), and adding a RUNTIME destination so the Windows DLL is installed — appear to already be in place. Before rebasing, it is probably worth re-testing your MSVC + vcpkg scenario against current main to see whether #810 is still reproducible at all.

One thing that does still look wrong on main

The two halves of the install disagree about the library directory. cpp/src/CMakeLists.txt hardcodes lib and bin, while cpp/CMakeLists.txt places the package config files using the GNU variable:

install(FILES "${PROJECT_BINARY_DIR}/graphar-config.cmake"
              "${PROJECT_BINARY_DIR}/graphar-config-version.cmake"
        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/graphar)

install(EXPORT graphar-targets
        FILE graphar-targets.cmake
        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/graphar)

include(GNUInstallDirs) is already present (cpp/CMakeLists.txt), and on distributions where CMAKE_INSTALL_LIBDIR is not plain lib (lib64 on Fedora/RHEL, lib/<triplet> on Debian multiarch) the package config lands in one tree while the library lands in another. Making cpp/src/CMakeLists.txt use ${CMAKE_INSTALL_LIBDIR}, ${CMAKE_INSTALL_BINDIR} and ${CMAKE_INSTALL_INCLUDEDIR} would be a small, self-contained follow-up, and a good scope for this PR after the rebase.

Style note for whatever survives

The diff comments the old calls out rather than deleting them:

-    install_graphar_target(graphar)
+   # install_graphar_target(graphar)

Commented-out code should be removed outright; the indentation also drops from four spaces to three on the first hunk, which cmake-format would flag.