[lldb] Use `GNUInstallDirs` to support custom installation dirs.

[Ericson2314]

Summary

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

[Ericson2314]

lldb/cmake/modules/AddLLDB.cmake

1

I think a problem with D115544 was that AddLLVM was assuming GNUInstallDirs yet downstream packages didn't yet include it.

By starting with "leaf" packages I side-step this issue somewhat, but I am still putting these here defensively so that downstream projects that might include these aren't broken, and the precedent is set.

[Ericson2314]

simplify

[Ericson2314]

1. Updating D115570: [lldb] Use GNUInstallDirs to support custom installation dirs. #
2. Enter a brief description of the changes included in this update.
3. The first line is used as subject, next lines as comment. #
4. If you intended to create a new revision, use:
5. $ arc diff --create

remove blank line we don't need to add

[Ericson2314]

Thanks, @compnerd!

lldb/CMakeLists.txt

 cmake_minimum_required(VERSION 3.13.4)
 
 # Add path for custom modules.
 set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules"
   )
 
 # If we are not building as part of LLVM, build LLDB as a standalone project,
 # using LLVM as an external library.
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(lldb)
+endif()
+
+include(GNUInstallDirs)
+
+if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   include(LLDBStandalone)
 
   set(CMAKE_CXX_STANDARD 14 CACHE STRING "C++ standard to conform to")
   set(CMAKE_CXX_STANDARD_REQUIRED YES)
   set(CMAKE_CXX_EXTENSIONS NO)
 endif()
 
 include(LLDBConfig)

lldb/cmake/modules/AddLLDB.cmake

+include(GNUInstallDirs)
 function(lldb_tablegen)
   # Syntax:
   # lldb_tablegen output-file [tablegen-arg ...] SOURCE source-file
   # [[TARGET cmake-target-name] [DEPENDS extra-dependency ...]]
   #
   # Generates a custom command for invoking tblgen as
   #
   # tblgen source-file -o=output-file tablegen-arg ...
)
 
   if(PARAM_SHARED)
     set(install_dest lib${LLVM_LIBDIR_SUFFIX})
     if(PARAM_INSTALL_PREFIX)
       set(install_dest ${PARAM_INSTALL_PREFIX})
     endif()
     # RUNTIME is relevant for DLL platforms, FRAMEWORK for macOS
     install(TARGETS ${name} COMPONENT ${name}
-      RUNTIME DESTINATION bin
+      RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
       LIBRARY DESTINATION ${install_dest}
       ARCHIVE DESTINATION ${install_dest}
       FRAMEWORK DESTINATION ${install_dest})
     if (NOT CMAKE_CONFIGURATION_TYPES)
       add_llvm_install_targets(install-${name}
                               DEPENDS ${name}
                               COMPONENT ${name})
     endif()

lldb/cmake/modules/LLDBConfig.cmake

 include_directories(BEFORE
   ${CMAKE_CURRENT_BINARY_DIR}/include
   ${CMAKE_CURRENT_SOURCE_DIR}/include
   )
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/
     COMPONENT lldb-headers
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     FILES_MATCHING
     PATTERN "*.h"
     PATTERN ".cmake" EXCLUDE
     )
 
   install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/include/
     COMPONENT lldb-headers
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     FILES_MATCHING
     PATTERN "*.h"
     PATTERN ".cmake" EXCLUDE
     )
 
   add_custom_target(lldb-headers)
   set_target_properties(lldb-headers PROPERTIES FOLDER "lldb misc")