Pass SDK paths explicitly when building Runtimes in macOS smoketest

As per https://gitlab.kitware.com/cmake/cmake/-/commit/7b195312919cbf69497af2514b91b55bd9a6da71
CMake 4.0 does not pass `-sdk` to compiler invocations if the user does
not provide `CMAKE_OSX_SYSROOT` -- this in turn causes failures in
linking.

Addresses rdar://163672815

Author: edymtt

CMakeLists.txt

@@ -1686,7 +1686,8 @@ if(SWIFT_ENABLE_NEW_RUNTIME_BUILD)
           -DCMAKE_COLOR_DIAGNOSTICS:BOOLEAN=${CMAKE_COLOR_DIAGNOSTICS}
           -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
           -DSwiftCore_INSTALL_NESTED_SUBDIR=YES
-          -DSwiftCore_ENABLE_CONCURRENCY=${build_concurrency})
+          -DSwiftCore_ENABLE_CONCURRENCY=${build_concurrency}
+          -DCMAKE_OSX_SYSROOT:PATH=${SWIFT_SDK_${sdk}_ARCH_${arch}_PATH})
       if(NOT ${CMAKE_CROSSCOMPILING})
         add_dependencies("${stdlib_target}-core" swift-frontend)
       endif()
@@ -1714,7 +1715,8 @@ if(SWIFT_ENABLE_NEW_RUNTIME_BUILD)
           -DCMAKE_COLOR_DIAGNOSTICS:BOOLEAN=${CMAKE_COLOR_DIAGNOSTICS}
           -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
           -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=TRUE
-          -DSwiftOverlay_ENABLE_CXX_INTEROP=TRUE)
+          -DSwiftOverlay_ENABLE_CXX_INTEROP=TRUE
+          -DCMAKE_OSX_SYSROOT:PATH=${SWIFT_SDK_${sdk}_ARCH_${arch}_PATH})
 
       ExternalProject_Add("${stdlib_target}-Supplemental"
         SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/Runtimes/Supplemental"
@@ -1739,7 +1741,8 @@ if(SWIFT_ENABLE_NEW_RUNTIME_BUILD)
           -DCMAKE_ASM_COMPILER_TARGET:STRING=${stdlib_target_triple}
           -DCMAKE_COLOR_DIAGNOSTICS:BOOLEAN=${CMAKE_COLOR_DIAGNOSTICS}
           -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
-          -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=TRUE)
+          -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=TRUE
+          -DCMAKE_OSX_SYSROOT:PATH=${SWIFT_SDK_${sdk}_ARCH_${arch}_PATH})
     endforeach()
   endforeach()
 endif()

Runtimes/Supplemental/CMakeLists.txt

@@ -42,6 +42,7 @@ set(COMMON_OPTIONS
   -DCMAKE_ASM_COMPILER_TARGET=${CMAKE_ASM_COMPILER_TARGET}
   -DCMAKE_Swift_COMPILER_TARGET=${CMAKE_Swift_COMPILER_TARGET}
   -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=${CMAKE_FIND_PACKAGE_PREFER_CONFIG}
+  -DCMAKE_OSX_SYSROOT:PATH=${CMAKE_OSX_SYSROOT}
   ${SwiftCore_DIR_FLAG}
   ${MAKE_PROGRAM_FLAG})