All lib installs target CMake install libdir

[corey-cole]

Summary

4 libraries previously targeted the lib directory in the build directory. This change modifies target location to match the other 55 libraries in the project.

Fixes #20709

Test plan

# Configure, build, and install
cmake -B cmake-out --preset linux -DCMAKE_BUILD_TYPE=Release -DEXECUTORCH_BUILD_XNNPACK=ON -DCMAKE_INSTALL_PREFIX="et-install" -DCMAKE_POSITION_INDEPENDENT_CODE=ON -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON -DEXECUTORCH_BUILD_EXTENSION_TENSOR=ON
cmake --build cmake-out -j15
cmake --install cmake-out --prefix et-install
# Confirm source directory isn't baked into release .cmake file (exit code 1)
grep -n 'cmake-out' et-install/lib/cmake/ExecuTorch/ExecuTorchTargets-release.cmake
# Confirm modified targets appear in installation lib directory
ls -l et-install/lib/libextension_evalue_util.a # exists
ls -l et-install/lib/libflatccrt.a # exists

cc @larryliu0820 @GregoryComer

[pytorch-bot]

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• ✅ login: corey-cole / name: Corey Cole (2d6bac4)

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[psiddh]

@claude review

[claude]

Claude finished @psiddh's task in 53s —— View job

---

Code Review

• Analyze the PR diff
• Verify CMAKE_INSTALL_LIBDIR availability and consistency with the rest of the project

---

LGTM ✅ — this is a clean, correct fix that resolves #20709.

What the change does

Four install(...) calls previously hardcoded DESTINATION ${CMAKE_BINARY_DIR}/lib, which pins the install location to the build tree rather than honoring CMAKE_INSTALL_PREFIX. This PR switches them to ${CMAKE_INSTALL_LIBDIR}, matching the other ~55 install targets across the project:

• devtools/bundled_program/CMakeLists.txt:54 — bundled_program
• devtools/etdump/CMakeLists.txt:66 — etdump, flatccrt
• extension/evalue_util/CMakeLists.txt:27 — extension_evalue_util
• third-party/CMakeLists.txt:190 — flatccrt

Correctness checks

• CMAKE_INSTALL_LIBDIR is defined at these points. The root CMakeLists.txt:110 runs include(GNUInstallDirs) before add_subdirectory(third-party) (line 274), schema (line 520), and the devtools/extension subdirectories, so the variable is populated wherever these installs run. No ordering hazard.
• Consistency confirmed. Every other install target in the repo (backends/*, extension/*, schema, configurations, etc.) already uses ${CMAKE_INSTALL_LIBDIR}. These four were the outliers.
• Fixes the reported bug. The old ${CMAKE_BINARY_DIR}/lib destination baked the source/build path into the exported ExecuTorchTargets config, breaking relocatable installs — exactly what the test plan's grep for cmake-out verifies is now gone.

Minor / non-blocking notes

1. Commit message — Move targets to is truncated/incomplete. Consider amending to something like Install libs to CMAKE_INSTALL_LIBDIR instead of build dir before merge. Per the repo's CLAUDE.md, please also disclose if this PR was authored with Claude.
2. release notes: label — the bot is asking for one; release notes: none is likely appropriate for a build-config fix (though packagers/downstream consumers do benefit, so release notes: build could be argued).
3. GNUInstallDirs default — CMAKE_INSTALL_LIBDIR defaults to lib (or lib64 on some 64-bit distros). That's the intended, standards-compliant behavior and is what the rest of the project already relies on, so no action needed — just flagging that installs on multilib systems may land in lib64/, which is correct.

Nice, well-scoped fix with a clear reproducible test plan. 👍
• feature/portable-install-fix