[bootstrap] Add the runtime library paths to [DY]LD_LIBRARY_PATHS so we use the just-built libswiftCore instead of the OS's copy. (#2806)

Author: mikeash

Utilities/bootstrap

@@ -616,7 +616,7 @@ def get_swiftpm_env_cmd(args):
         os.path.join(args.llbuild_build_dir, "lib"),
         os.path.join(args.yams_build_dir, "lib"),
         os.path.join(args.swift_driver_build_dir, "lib"),
-    ])
+    ] + args.target_info["paths"]["runtimeLibraryPaths"])
 
     if platform.system() == 'Darwin':
         env_cmd.append("DYLD_LIBRARY_PATH=%s" % libs_joined)