unittests: fixes for Swift's custom build system

Because we do not have proper libraries in our system, we cannot attach
interface link libraries, especially in light of the
incorporate_object_library implementation.  Explicitly add the
dependency on DbgHelp for the unit tests.

Author: compnerd

unittests/runtime/CMakeLists.txt

@@ -30,6 +30,8 @@ if(("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "${SWIFT_PRIMARY_VARIANT_SDK}") AND
     list(APPEND PLATFORM_TARGET_LINK_LIBRARIES
       ${EXECINFO_LIBRARY}
       )
+  elseif(SWIFT_HOST_VARIANT STREQUAL windows)
+    list(APPEND PLATFORM_TARGET_LINK_LIBRARIES DbgHelp)
   endif()
 
   add_swift_unittest(SwiftRuntimeTests

unittests/runtime/LongTests/CMakeLists.txt

@@ -25,6 +25,8 @@ if(("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "${SWIFT_PRIMARY_VARIANT_SDK}") AND
     list(APPEND PLATFORM_TARGET_LINK_LIBRARIES
       ${EXECINFO_LIBRARY}
       )
+  elseif(SWIFT_HOST_VARIANT STREQUAL windows)
+    list(APPEND PLATFORM_TARGET_LINK_LIBRARIES DbgHelp)
   endif()
 
   add_swift_unittest(SwiftRuntimeLongTests