Rollup merge of #49432 - nabijaczleweli:master, r=michaelwoerister
Flush executables to disk after linkage
A problem caused by not doing so in Chrome has been reported [here](https://randomascii.wordpress.com/2018/02/25/compiler-bug-linker-bug-windows-kernel-bug/amp/).
`File::sync_all()` calls `FlushFileBuffers()` down the line, causing potentially unflushed buffers on high I/O-load systems to flush and preventing nasty non-reproducible bugs.