Copy libsleef.a from a lib64 directory

[abrown]

On my machine, the sleef library builds within a lib64 directory, not lib directory. Let's see if this causes any CI issues; if so, this will need to be more sophisticated.

[Copilot]

Pull request overview

This PR changes the SLEEF library copy path from lib to lib64 to accommodate the author's build environment where SLEEF installs to lib64 instead of lib. However, the library installation directory is platform-dependent, and this hardcoded change will break builds on other platforms.

Changes:

• Modified the SLEEF library copy path from lib to lib64 in the CMake ExternalProject configuration

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[Copilot]

Hardcoding the library path to lib64 will break builds on platforms where SLEEF installs to lib instead of lib64. The library directory varies by platform: Linux distributions like RHEL/Fedora use lib64, while Ubuntu/Debian and macOS typically use lib.

Consider using conditional logic to check for the existence of the library in both locations. For example:

# Try lib64 first, fall back to lib
if(EXISTS ${SLEEF_INSTALL_DIR}/lib64/libsleef.a)
  set(SLEEF_LIB_PATH ${SLEEF_INSTALL_DIR}/lib64/libsleef.a)
else()
  set(SLEEF_LIB_PATH ${SLEEF_INSTALL_DIR}/lib/libsleef.a)
endif()

ExternalProject_Add_Step(sleef copy_lib
  COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
  COMMAND ${CMAKE_COMMAND} -E copy
          ${SLEEF_LIB_PATH}
          ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}
  DEPENDEES install
  ALWAYS 1
)

Alternatively, you could pass -DCMAKE_INSTALL_LIBDIR=lib in the CMAKE_ARGS to force SLEEF to always install to lib, or use CMake's GNUInstallDirs module to determine the correct library directory based on the platform.