Move msvc libs to core

Author: ChrisDenton

library/core/src/lib.rs

@@ -178,6 +178,7 @@
 #![feature(ip_bits)]
 #![feature(is_ascii_octdigit)]
 #![feature(isqrt)]
+#![feature(link_cfg)]
 #![feature(maybe_uninit_uninit_array)]
 #![feature(non_null_convenience)]
 #![feature(offset_of_enum)]
@@ -468,3 +469,12 @@ pub mod simd {
 }
 
 include!("primitive_docs.rs");
+
+#[cfg(all(windows, target_env = "msvc"))]
+#[link(
+    name = "/defaultlib:msvcrt",
+    modifiers = "+verbatim",
+    cfg(not(target_feature = "crt-static"))
+)]
+#[link(name = "/defaultlib:libcmt", modifiers = "+verbatim", cfg(target_feature = "crt-static"))]
+extern "C" {}