Disable rpath for the bootstrap build with CMake.

--- a/Sources/PackageDescription/CMakeLists.txt
+++ b/Sources/PackageDescription/CMakeLists.txt
@@ -27,14 +27,11 @@
   $<$<COMPILE_LANGUAGE:Swift>:-package-description-version$<SEMICOLON>999.0>)
 
 if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
-  target_link_options(PackageDescription PRIVATE
-    "SHELL:-Xlinker -install_name -Xlinker @rpath/libPackageDescription.dylib")
 endif()
 
 set_target_properties(PackageDescription PROPERTIES
     Swift_MODULE_NAME PackageDescription
     Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
-    INSTALL_NAME_DIR \\@rpath
     OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
     OUTPUT_NAME PackageDescription
     ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
--- a/Sources/PackagePlugin/CMakeLists.txt
+++ b/Sources/PackagePlugin/CMakeLists.txt
@@ -29,14 +29,11 @@ if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
   set(SWIFT_INTERFACE_PATH ${CMAKE_BINARY_DIR}/pm/PluginAPI/PackagePlugin.swiftinterface)
   target_compile_options(PackagePlugin PUBLIC
     $<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${SWIFT_INTERFACE_PATH}>)
-  target_link_options(PackagePlugin PRIVATE
-    "SHELL:-Xlinker -install_name -Xlinker @rpath/libPackagePlugin.dylib")
 endif()
 
 set_target_properties(PackagePlugin PROPERTIES
   Swift_MODULE_NAME PackagePlugin
   Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/pm/PluginAPI
-  INSTALL_NAME_DIR \\@rpath
   OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/PluginAPI
   OUTPUT_NAME PackagePlugin
   ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/PluginAPI