Build the import lib with `_ENFORCE_ONLY_CORE_HEADERS` (#3621)

stl/CMakeLists.txt

@@ -584,7 +584,7 @@ function(add_stl_dlls D_SUFFIX REL_OR_DBG)
 
     # import library 'statics'
     add_library(msvcp${D_SUFFIX}_implib_objects OBJECT ${IMPLIB_SOURCES})
-    target_compile_definitions(msvcp${D_SUFFIX}_implib_objects PRIVATE _DLL)
+    target_compile_definitions(msvcp${D_SUFFIX}_implib_objects PRIVATE _DLL _ENFORCE_ONLY_CORE_HEADERS)
     target_compile_options(msvcp${D_SUFFIX}_implib_objects PRIVATE /EHsc) # No /GL!
     target_stl_compile_options(msvcp${D_SUFFIX}_implib_objects ${REL_OR_DBG})
 

stl/src/locale0.cpp

@@ -7,6 +7,8 @@
 // MAJOR LIMITATIONS apply to what can be included here!
 // Before editing this file, read: /docs/import_library.md
 
+#undef _ENFORCE_ONLY_CORE_HEADERS // TRANSITION, <xfacet> should be a core header
+
 #include <crtdbg.h>
 #include <internal_shared.h>
 #include <xatomic.h>

stl/src/nothrow.cpp

@@ -11,8 +11,10 @@
 #undef MRTDLL
 #endif
 
-#include <new>
-_STD_BEGIN
+#include <yvals_core.h>
 
-const nothrow_t nothrow = nothrow_t(); // define nothrow
+#include <vcruntime_new.h>
+
+_STD_BEGIN
+const nothrow_t nothrow = nothrow_t();
 _STD_END