[CMake] Allow overriding lib dir suffix independently from LLVM

[phosek]

Summary

This matches the options already supported by libc++ and libc++abi.

[jroelofs]

LGTM

CMakeLists.txt

 option(LIBUNWIND_ENABLE_SHARED "Build libunwind as a shared library." ON)
 option(LIBUNWIND_ENABLE_STATIC "Build libunwind as a static library." ON)
 option(LIBUNWIND_ENABLE_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF)
 option(LIBUNWIND_ENABLE_ARM_WMMX "Enable unwinding support for ARM WMMX registers." OFF)
 option(LIBUNWIND_ENABLE_THREADS "Build libunwind with threading support." ON)
 option(LIBUNWIND_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 option(LIBUNWIND_INCLUDE_DOCS "Build the libunwind documentation." ${LLVM_INCLUDE_DOCS})
 
+set(LIBUNWIND_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
+    "Define suffix of library directory name (32/64)")
 set(LIBUNWIND_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
 set(LIBUNWIND_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBUNWIND_SYSROOT "" CACHE PATH "Sysroot for cross compiling.")
 
 if (NOT LIBUNWIND_ENABLE_SHARED AND NOT LIBUNWIND_ENABLE_STATIC)
   message(FATAL_ERROR "libunwind must be built as either a shared or static library.")
 endif()
 
set(CMAKE_MODULE_PATH
     ${CMAKE_MODULE_PATH})
 
 set(LIBUNWIND_COMPILER    ${CMAKE_CXX_COMPILER})
 set(LIBUNWIND_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
 set(LIBUNWIND_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
 if (LLVM_LIBRARY_OUTPUT_INTDIR)
   set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR})
 else()
-  set(LIBUNWIND_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
+  set(LIBUNWIND_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBUNWIND_LIBDIR_SUFFIX})
 endif()
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LIBUNWIND_LIBRARY_DIR})
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${LIBUNWIND_LIBRARY_DIR})
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${LIBUNWIND_LIBRARY_DIR})
 
 set(LIBUNWIND_INSTALL_PREFIX "" CACHE STRING
     "Define libunwind destination prefix.")

src/CMakeLists.txt

set_target_properties(unwind_static
                           OUTPUT_NAME   "unwind")
   list(APPEND LIBUNWIND_TARGETS "unwind_static")
 endif()
 
 # Add a meta-target for both libraries.
 add_custom_target(unwind DEPENDS ${LIBUNWIND_TARGETS})
 
 install(TARGETS ${LIBUNWIND_TARGETS}
-  LIBRARY DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LLVM_LIBDIR_SUFFIX}
-  ARCHIVE DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LLVM_LIBDIR_SUFFIX})
+  LIBRARY DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX}
+  ARCHIVE DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LIBUNWIND_LIBDIR_SUFFIX})