[libcxx][libcxxabi][libunwind][cmake] Use GNUInstallDirs to support…

… custom installation dirs

I am breaking apart D99484 so the cause of build failures is easier to
understand.

Differential Revision: https://reviews.llvm.org/D117417

libcxx/CMakeLists.txt

@@ -10,6 +10,8 @@ endif()
 #===============================================================================
 cmake_minimum_required(VERSION 3.13.4)
 
+include(GNUInstallDirs)
+
 set(LLVM_COMMON_CMAKE_UTILS "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
 
 # Add path for custom modules
@@ -412,9 +414,9 @@ endif ()
 # TODO: Projects that depend on libc++ should use LIBCXX_GENERATED_INCLUDE_DIR
 # instead of hard-coding include/c++/v1.
 
-set(LIBCXX_INSTALL_INCLUDE_DIR "include/c++/v1" CACHE PATH
+set(LIBCXX_INSTALL_INCLUDE_DIR "${CMAKE_INSTALL_INCLUDEDIR}/c++/v1" CACHE PATH
     "Path where target-agnostic libc++ headers should be installed.")
-set(LIBCXX_INSTALL_RUNTIME_DIR bin CACHE PATH
+set(LIBCXX_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
     "Path where built libc++ runtime libraries should be installed.")
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
@@ -423,7 +425,7 @@ if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(LIBCXX_GENERATED_INCLUDE_TARGET_DIR "${LLVM_BINARY_DIR}/include/${LLVM_DEFAULT_TARGET_TRIPLE}/c++/v1")
   set(LIBCXX_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE} CACHE PATH
       "Path where built libc++ libraries should be installed.")
-  set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "include/${LLVM_DEFAULT_TARGET_TRIPLE}/c++/v1" CACHE PATH
+  set(LIBCXX_INSTALL_INCLUDE_TARGET_DIR "${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++/v1" CACHE PATH
       "Path where target-specific libc++ headers should be installed.")
   if(LIBCXX_LIBDIR_SUBDIR)
     string(APPEND LIBCXX_LIBRARY_DIR /${LIBCXX_LIBDIR_SUBDIR})

libcxx/cmake/Modules/HandleLibCXXABI.cmake

@@ -1,8 +1,9 @@
-
 #===============================================================================
 # Add an ABI library if appropriate
 #===============================================================================
 
+include(GNUInstallDirs)
+
 #
 # _setup_abi: Set up the build to use an ABI library
 #
@@ -63,7 +64,7 @@ macro(setup_abi_lib abidefines abishared abistatic abifiles abidirs)
 
         if (LIBCXX_INSTALL_HEADERS)
           install(FILES "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}"
-            DESTINATION include/c++/v1/${dstdir}
+            DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/c++/v1/${dstdir}"
             COMPONENT cxx-headers
             PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
             )

libcxxabi/CMakeLists.txt

@@ -10,6 +10,8 @@ endif()
 
 cmake_minimum_required(VERSION 3.13.4)
 
+include(GNUInstallDirs)
+
 set(LLVM_COMMON_CMAKE_UTILS "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
 
 # Add path for custom modules
@@ -210,7 +212,7 @@ set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}
   )
 
-set(LIBCXXABI_INSTALL_RUNTIME_DIR bin CACHE PATH
+set(LIBCXXABI_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
     "Path where built libc++abi runtime libraries should be installed.")
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)

libunwind/CMakeLists.txt

@@ -8,6 +8,8 @@ endif()
 
 cmake_minimum_required(VERSION 3.13.4)
 
+include(GNUInstallDirs)
+
 set(LLVM_COMMON_CMAKE_UTILS "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
 
 # Add path for custom modules
@@ -137,9 +139,9 @@ set(CMAKE_MODULE_PATH
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
     ${CMAKE_MODULE_PATH})
 
-set(LIBUNWIND_INSTALL_INCLUDE_DIR include CACHE PATH
+set(LIBUNWIND_INSTALL_INCLUDE_DIR "${CMAKE_INSTALL_INCLUDEDIR}" CACHE PATH
     "Path where built libunwind headers should be installed.")
-set(LIBUNWIND_INSTALL_RUNTIME_DIR bin CACHE PATH
+set(LIBUNWIND_INSTALL_RUNTIME_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
     "Path where built libunwind runtime libraries should be installed.")
 
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)