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

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

Reviewed By: compnerd

Differential Revision: https://reviews.llvm.org/D115570

lldb/CMakeLists.txt

@@ -1,5 +1,7 @@
 cmake_minimum_required(VERSION 3.13.4)
 
+include(GNUInstallDirs)
+
 # Add path for custom modules.
 set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}

lldb/cmake/modules/AddLLDB.cmake

@@ -1,3 +1,5 @@
+include(GNUInstallDirs)
+
 function(lldb_tablegen)
   # Syntax:
   # lldb_tablegen output-file [tablegen-arg ...] SOURCE source-file
@@ -113,7 +115,7 @@ function(add_lldb_library name)
     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})

lldb/cmake/modules/LLDBConfig.cmake

@@ -231,7 +231,7 @@ include_directories(BEFORE
 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
@@ -239,7 +239,7 @@ if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
 
   install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/include/
     COMPONENT lldb-headers
-    DESTINATION include
+    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
     FILES_MATCHING
     PATTERN "*.h"
     PATTERN ".cmake" EXCLUDE