Rollup merge of #81598 - sivadeilra:windows_dll_imports_fix_x86, r=m-ou-se

Rollup merge of #81598 - sivadeilra:windows_dll_imports_fix_x86, r=m-ou-se

Fix calling convention for CRT startup

My PR #81478 used the wrong calling convention for a set of
functions that are called by the CRT. These functions need to use
`extern "C"`.

This would only affect x86, which is the only target (that I know of)
that has multiple calling conventions.

```@bors``` r? ```@m-ou-se```