Pass platform name in SwiftCore link

The platform name was hard-coded to `linux`. The target name when
building for FreeBSD is `swiftCore-freebsd-${arch}` resulting in a build
failure due to the missing swiftCore-linux-${arch} target.

Author: etcwilde

lldb/cmake/modules/AddLLDB.cmake

@@ -221,8 +221,8 @@ function(add_properties_for_swift_modules target reldir)
       set_property(TARGET ${target} APPEND PROPERTY INSTALL_RPATH "${SWIFT_INSTALL_RPATH}")
     elseif (CMAKE_SYSTEM_NAME MATCHES "Linux|Android|OpenBSD|FreeBSD")
       string(REGEX MATCH "^[^-]*" arch ${LLVM_TARGET_TRIPLE})
-      target_link_libraries(${target} PRIVATE swiftCore-linux-${arch})
       string(TOLOWER ${CMAKE_SYSTEM_NAME} platform)
+      target_link_libraries(${target} PRIVATE swiftCore-${platform}-${arch})
       set(SWIFT_BUILD_RPATH "${LLDB_SWIFT_LIBS}/${platform}")
       set(SWIFT_INSTALL_RPATH "$ORIGIN/${reldir}lib/swift/${platform}")
       set_property(TARGET ${target} APPEND PROPERTY BUILD_RPATH "${SWIFT_BUILD_RPATH}")