[lld][CMake] Use GNUInstallDirs to support custom installation dirs

Extracted from D99484. My new plan is to start from the outside and work
inward.

Reviewed By: stephenneuendorffer

Differential Revision: https://reviews.llvm.org/D115568

lld/CMakeLists.txt

@@ -1,3 +1,5 @@
+include(GNUInstallDirs)
+
 # Check if lld is built as a standalone project.
 if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(lld)
@@ -34,8 +36,8 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   set(LLVM_MAIN_INCLUDE_DIR ${MAIN_INCLUDE_DIR} CACHE PATH "path to llvm/include")
   set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
 
-  file(TO_CMAKE_PATH ${LLVM_OBJ_ROOT} LLVM_BINARY_DIR)
-  file(TO_CMAKE_PATH ${LLVM_CMAKE_DIR} LLVM_CMAKE_DIR)
+  file(TO_CMAKE_PATH "${LLVM_OBJ_ROOT}" LLVM_BINARY_DIR)
+  file(TO_CMAKE_PATH "${LLVM_CMAKE_DIR}" LLVM_CMAKE_DIR)
 
   if(NOT EXISTS "${LLVM_CMAKE_DIR}/LLVMConfig.cmake")
     message(FATAL_ERROR "LLVMConfig.cmake not found")
@@ -151,7 +153,11 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
 "`CMakeFiles'. Please delete them.")
 endif()
 
-list (APPEND CMAKE_MODULE_PATH "${LLD_SOURCE_DIR}/cmake/modules")
+# Add path for custom modules.
+list(INSERT CMAKE_MODULE_PATH 0
+  "${LLD_SOURCE_DIR}/cmake/modules"
+  "${LLD_SOURCE_DIR}/../cmake/Modules"
+  )
 
 include(AddLLD)
 
@@ -188,7 +194,7 @@ include_directories(BEFORE
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     FILES_MATCHING
     PATTERN "*.h"
     )

lld/cmake/modules/AddLLD.cmake

@@ -1,3 +1,4 @@
+include(GNUInstallDirs)
 include(LLVMDistributionSupport)
 
 macro(add_lld_library name)
@@ -19,7 +20,7 @@ macro(add_lld_library name)
       ${export_to_lldtargets}
       LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
       ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
-      RUNTIME DESTINATION bin)
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
 
     if (${ARG_SHARED} AND NOT CMAKE_CONFIGURATION_TYPES)
       add_llvm_install_targets(install-${name}
@@ -46,7 +47,7 @@ macro(add_lld_tool name)
     get_target_export_arg(${name} LLD export_to_lldtargets)
     install(TARGETS ${name}
       ${export_to_lldtargets}
-      RUNTIME DESTINATION bin
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
       COMPONENT ${name})
 
     if(NOT CMAKE_CONFIGURATION_TYPES)

lld/cmake/modules/CMakeLists.txt

@@ -1,3 +1,5 @@
+include(ExtendPath)
+
 # Generate a list of CMake library targets so that other CMake projects can
 # link against them. LLVM calls its version of this file LLVMExports.cmake, but
 # the usual CMake convention seems to be ${Project}Targets.cmake.
@@ -40,7 +42,7 @@ endforeach(p)
 set(LLD_CONFIG_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLD_INSTALL_PACKAGE_DIR}")
 set(LLD_CONFIG_LLVM_CMAKE_DIR "\${LLD_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
 get_config_exports_includes(LLD LLD_CONFIG_INCLUDE_EXPORTS)
-set(LLD_CONFIG_INCLUDE_DIRS "\${LLD_INSTALL_PREFIX}/include")
+extend_path(LLD_CONFIG_INCLUDE_DIRS "\${LLD_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
 configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/LLDConfig.cmake.in
   ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/LLDConfig.cmake

lld/tools/lld/CMakeLists.txt

@@ -20,7 +20,7 @@ target_link_libraries(lld
   )
 
 install(TARGETS lld
-  RUNTIME DESTINATION bin)
+  RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
 
 if(NOT LLD_SYMLINKS_TO_CREATE)
   set(LLD_SYMLINKS_TO_CREATE