[libcxx] Link to fewer MSVC CRT libraries

[mstorsjo]

Summary

The library msvcrt.lib pulls in ucrt.lib and vcruntime.lib anyway,
there's no need to manually link against the individual dependencies.

This matches how the tests link against libraries - they only link
against msvcrt and msvcprt, not directly against ucrt and vcruntime.

[Mordante]

Since the CI is happy, LGTM!

libcxx/CMakeLists.txt

# all libraries but c++ have to be added in manually.
 
   if (MSVC)
     if (uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
       set(LIB_SUFFIX "d")
     else()
       set(LIB_SUFFIX "")
     endif()
 
-    target_link_libraries(${target} PRIVATE ucrt${LIB_SUFFIX}) # Universal C runtime
-    target_link_libraries(${target} PRIVATE vcruntime${LIB_SUFFIX}) # C++ runtime
     target_link_libraries(${target} PRIVATE msvcrt${LIB_SUFFIX}) # C runtime startup files
     target_link_libraries(${target} PRIVATE msvcprt${LIB_SUFFIX}) # C++ standard library. Required for exception_ptr internals.
     # Required for standards-complaint wide character formatting functions
     # (e.g. `printfw`/`scanfw`)
     target_link_libraries(${target} PRIVATE iso_stdio_wide_specifiers)
   endif()
 
   if (ANDROID AND ANDROID_PLATFORM_LEVEL LESS 21)