[lldb][Swift][CMake] Correct RUNPATH in Linux builds

* When LLDB_BUILD_FRAMEWORK is not enabled, liblldb is built/installed
  in 'lib/'. Pass the correct path to 'add_properties_for_swift_modules
* '$ORIGIN' instead of '@loader_path' in Linux-like platforms

(cherry picked from commit 680e5ba)

Author: rintaro

lldb/cmake/modules/AddLLDB.cmake

@@ -224,10 +224,17 @@ function(add_properties_for_swift_modules target reldir)
     set_property(TARGET ${target} APPEND PROPERTY INSTALL_RPATH "${SWIFT_INSTALL_RPATH}")
 
     if (SWIFT_SWIFT_PARSER)
-      set_property(TARGET ${target}
-        APPEND PROPERTY BUILD_RPATH "@loader_path/${build_reldir}lib/swift/host")
-      set_property(TARGET ${target}
-        APPEND PROPERTY INSTALL_RPATH "@loader_path/${reldir}lib/swift/host")
+      if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
+        set_property(TARGET ${target}
+          APPEND PROPERTY BUILD_RPATH "@loader_path/${build_reldir}lib/swift/host")
+        set_property(TARGET ${target}
+          APPEND PROPERTY INSTALL_RPATH "@loader_path/${reldir}lib/swift/host")
+      elseif (CMAKE_SYSTEM_NAME MATCHES "Linux|Android|OpenBSD|FreeBSD")
+        set_property(TARGET ${target}
+          APPEND PROPERTY BUILD_RPATH "$ORIGIN/${build_reldir}lib/swift/host")
+        set_property(TARGET ${target}
+          APPEND PROPERTY INSTALL_RPATH "$ORIGIN/${reldir}lib/swift/host")
+      endif()
     endif()
   endif()
 endfunction()

lldb/source/API/CMakeLists.txt

@@ -154,7 +154,11 @@ endif()
 # BEGIN Swift Mods
 # Note that add_properties_for_swift_modules appends RPATHs so it's critical
 # that this is called after lldb_setup_rpaths.
-add_properties_for_swift_modules(liblldb "../../../../../../usr/" "../../../../")
+if(LLDB_BUILD_FRAMEWORK)
+  add_properties_for_swift_modules(liblldb "../../../../../../usr/" "../../../../")
+else()
+  add_properties_for_swift_modules(liblldb "../")
+endif()
 # END Swift Mods
 
 if(LLDB_ENABLE_PYTHON)