Modularize CMake Build [5B/N] (#3451)

Summary:
X-link: facebookresearch/FBGEMM#550

- Set RPATh to be just `$ORIGIN`

Pull Request resolved: #3451

Reviewed By: spcyppt

Differential Revision: D66842181

Pulled By: q10

fbshipit-source-id: 6e9af4dbc0f7b3c62d7d0673a51aef95c7845ed9

.github/scripts/fbgemm_gpu_postbuild.bash

@@ -8,16 +8,20 @@
 echo "################################################################################"
 echo "[CMAKE] Running post-build script ..."
 
-# Print directory
-pwd
+TARGET=$1
+SET_RPATH_TO_ORIGIN=$2
+echo "Target file: ${TARGET}"
 
-# List all generated .SO files
-find . -name '*.so'
-
-# Remove errant RPATHs from the .SO
+# Set or remove RPATHs for the .SO
 # https://github.com/pytorch/FBGEMM/issues/3098
 # https://github.com/NixOS/patchelf/issues/453
-find . -name '*.so' -print0 | xargs -0 patchelf --remove-rpath
+if [ "${SET_RPATH_TO_ORIGIN}" != "" ]; then
+    echo "Resetting RPATH to \$ORIGIN ..."
+    patchelf --force-rpath --set-rpath "\$ORIGIN" "${TARGET}" || exit 1
+else
+    echo "Removing all RPATHs ..."
+    patchelf --remove-rpath "${TARGET}" || exit 1
+fi
 
-echo "[CMAKE] Removed errant RPATHs"
+readelf -d "${TARGET}" | grep -i rpath
 echo "################################################################################"

cmake/modules/GpuCppLibrary.cmake

@@ -290,16 +290,21 @@ function(gpu_cpp_library)
     # Post-Build Steps
     ############################################################################
 
-    # NOTE: Fix this in future PR
+    if (args_DEPS)
+        # Only set this if the library has dependencies that we also build,
+        # otherwise we will hit the following error:
+        #   `No valid ELF RPATH or RUNPATH entry exists in the file`
+        set(set_rpath_to_origin 1)
+    endif()
 
     # Add a post-build step to remove errant RPATHs from the .SO
-    # add_custom_target(${lib_name}_postbuild ALL
-    #     DEPENDS
-    #     WORKING_DIRECTORY ${OUTPUT_DIR}
-    #     COMMAND bash ${FBGEMM}/.github/scripts/fbgemm_gpu_postbuild.bash)
+    add_custom_target(${lib_name}_postbuild ALL
+        DEPENDS
+        WORKING_DIRECTORY ${OUTPUT_DIR}
+        COMMAND bash ${FBGEMM}/.github/scripts/fbgemm_gpu_postbuild.bash $<TARGET_FILE:${lib_name}> ${set_rpath_to_origin})
 
-    # # Set the post-build steps to run AFTER the build completes
-    # add_dependencies(${lib_name}_postbuild ${lib_name})
+    # Set the post-build steps to run AFTER the build completes
+    add_dependencies(${lib_name}_postbuild ${lib_name})
 
     ############################################################################
     # Set the Output Variable(s)