[build] Adjust install name for Differentiation and Concurrency

This way we match the way we build other Swift libraries, to allow the
dylib to have an absolute install name and at the same time be found
when used as part of a local toolchain (e.g. #31183)

Author: edymtt

stdlib/public/Concurrency/CMakeLists.txt

@@ -13,6 +13,7 @@
 add_swift_target_library(swift_Concurrency ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   Actor.swift
   PartialAsyncTask.swift
+  "${SWIFT_SOURCE_DIR}/stdlib/linker-support/magic-symbols-for-install-name.c"
 
   SWIFT_MODULE_DEPENDS_OSX Darwin
   SWIFT_MODULE_DEPENDS_IOS Darwin
@@ -29,5 +30,4 @@ add_swift_target_library(swift_Concurrency ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} I
     ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
     -parse-stdlib
   LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
-  DARWIN_INSTALL_NAME_DIR "@rpath"
   INSTALL_IN_COMPONENT stdlib)

stdlib/public/Differentiation/CMakeLists.txt

@@ -17,6 +17,7 @@ add_swift_target_library(swift_Differentiation ${SWIFT_STDLIB_LIBRARY_BUILD_TYPE
   AnyDifferentiable.swift
   ArrayDifferentiation.swift
   OptionalDifferentiation.swift
+  "${SWIFT_SOURCE_DIR}/stdlib/linker-support/magic-symbols-for-install-name.c"
 
   GYB_SOURCES
     FloatingPointDifferentiation.swift.gyb
@@ -38,5 +39,4 @@ add_swift_target_library(swift_Differentiation ${SWIFT_STDLIB_LIBRARY_BUILD_TYPE
     ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
     -parse-stdlib
   LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
-  DARWIN_INSTALL_NAME_DIR "@rpath"
   INSTALL_IN_COMPONENT stdlib)