[Runtimes][CMake] use config mode first in Supplemental build in CI

In this configuration we want to pull dependencies from the current
build, not from the underlying SDK.

Addresses rdar://151784135

Author: edymtt

CMakeLists.txt

@@ -1684,7 +1684,8 @@ if(SWIFT_ENABLE_NEW_RUNTIME_BUILD)
           -DCMAKE_C_COMPILER_TARGET:STRING=${stdlib_target_triple}
           -DCMAKE_CXX_COMPILER_TARGET:STRING=${stdlib_target_triple}
           -DCMAKE_COLOR_DIAGNOSTICS:BOOLEAN=${CMAKE_COLOR_DIAGNOSTICS}
-          -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM})
+          -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
+          -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=TRUE)
     endforeach()
   endforeach()
 endif()

Runtimes/Supplemental/CMakeLists.txt

@@ -35,6 +35,7 @@ set(COMMON_OPTIONS
   -DCMAKE_C_COMPILER_TARGET=${CMAKE_C_COMPILER_TARGET}
   -DCMAKE_CXX_COMPILER_TARGET=${CMAKE_CXX_COMPILER_TARGET}
   -DCMAKE_Swift_COMPILER_TARGET=${CMAKE_Swift_COMPILER_TARGET}
+  -DCMAKE_FIND_PACKAGE_PREFER_CONFIG=${CMAKE_FIND_PACKAGE_PREFER_CONFIG}
   ${SwiftCore_DIR_FLAG}
   ${MAKE_PROGRAM_FLAG})