[libunwind][CMake] Add install path variable to allow overriding the destination

[phosek]

Summary

This is going to be used by the runtime build in the multi-target setup to allow using different install prefix for each target.

[beanz]

CMakeLists.txt

167

We need to have some enforcement that this is either empty or ends in "/" otherwise the behavior will be unintuitive. If you add that to all three of the patches this will be good.

That enforcement could be something like I sent you a while back, or it could be a CMake error. I just want to make it hard to misuse this feature.

[phosek]

@beanz I've added the error check in all three patches, can you take a look again?

[beanz]

LGTM!

CMakeLists.txt

set(CMAKE_MODULE_PATH
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
     ${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})
 set(LIBUNWIND_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
 
+set(LIBUNWIND_INSTALL_PREFIX "" CACHE STRING
+    "Define libunwind destination prefix.")
+
 set(LIBUNWIND_C_FLAGS "")
 set(LIBUNWIND_CXX_FLAGS "")
 set(LIBUNWIND_COMPILE_FLAGS "")
 set(LIBUNWIND_LINK_FLAGS "")
 
 # Get required flags.
 macro(append_if list condition var)
   if (${condition})

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 ${LIBUNWIND_TARGETS}
-        LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
-        ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX})
+  LIBRARY DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LLVM_LIBDIR_SUFFIX}
+  ARCHIVE DESTINATION ${LIBUNWIND_INSTALL_PREFIX}lib${LLVM_LIBDIR_SUFFIX})