[lld][cmake] Fix BUILD_SHARED_LIBS installation

[labath]

Summary

This fixes a regression caused by D28397, which switched lld from using
add_llvm_library to llvm_add_library. The latter does not automatically set up
install rules for libraries, as it's expected the project will set them up
manually based on its own needs.

This adds the install rules to add_lld_library for lld. They were inspired by
the similar add_clang_library macro in clang.

[davidlt]

Looks like this resolves issues with my builds:

a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/bin/lld-link
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/bin/lld
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldDriver.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldConfig.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldReaderWriter.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldMachO.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCOFF.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCore.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldReaderWriter.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldMachO.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldYAML.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldDriver.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldReaderWriter.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldELF.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCOFF.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldMachO.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldYAML.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCore.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldELF.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldDriver.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldELF.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldConfig.so.4
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCore.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldConfig.so.4.0.0
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldYAML.so
a/slc6_amd64_gcc700/external/llvm/4.0.0-cms3/lib64/liblldCOFF.so

[mgorny]

Oh, and I thought that it was a feature since lld was linked statically anyway! ;-D

[labath]

In D29007#654540, @mgorny wrote:

Oh, and I thought that it was a feature since lld was linked statically anyway! ;-D

BUILD_SHARED_LIBS is not a recommended way for deployment of llvm http://llvm.org/docs/CMake.html, but it seems it is used nonetheless.

cmake/modules/AddLLD.cmake

 macro(add_lld_library name)
-  llvm_add_library(${name} ${ARGN})
+  cmake_parse_arguments(ARG
+    "SHARED"
+    ""
+    ""
+    ${ARGN})
+  if(ARG_SHARED)
+    set(ARG_ENABLE_SHARED SHARED)
+  endif()
+  llvm_add_library(${name} ${ARG_ENABLE_SHARED} ${ARG_UNPARSED_ARGUMENTS})
   set_target_properties(${name} PROPERTIES FOLDER "lld libraries")
+
+  if (LLD_BUILD_TOOLS)
+    if(${name} IN_LIST LLVM_DISTRIBUTION_COMPONENTS OR
+        NOT LLVM_DISTRIBUTION_COMPONENTS)
+      set(export_to_lldtargets EXPORT lldTargets)
+      set_property(GLOBAL PROPERTY LLD_HAS_EXPORTS True)
+    endif()
+
+    install(TARGETS ${name}
+      COMPONENT ${name}
+      ${export_to_lldtargets}
+      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+      RUNTIME DESTINATION bin)
+
+    if (${ARG_SHARED} AND NOT CMAKE_CONFIGURATION_TYPES)
+      add_custom_target(install-${name}
+        DEPENDS ${name}
+        COMMAND "${CMAKE_COMMAND}"
+          -DCMAKE_INSTALL_COMPONENT=${name}
+          -P "${CMAKE_BINARY_DIR}/cmake_install.cmake")
+    endif()
+    set_property(GLOBAL APPEND PROPERTY LLD_EXPORTS ${name})
+  endif()
 endmacro(add_lld_library)
 
 macro(add_lld_executable name)
   add_llvm_executable(${name} ${ARGN})
   set_target_properties(${name} PROPERTIES FOLDER "lld executables")
 endmacro(add_lld_executable)
 
 macro(add_lld_tool name)