Merge pull request #4790 from rudis/devel-mkstemp

posix: add mkstemp

lib/posix/posix.nim

@@ -2653,6 +2653,12 @@ proc poll*(a1: ptr TPollfd, a2: Tnfds, a3: int): cint {.
 proc realpath*(name, resolved: cstring): cstring {.
   importc: "realpath", header: "<stdlib.h>".}
 
+proc mkstemp*(tmpl: cstring): cint {.importc, header: "<stdlib.h>".}
+  ## Create a temporary file.
+  ##
+  ## **Warning**: The `tmpl` argument is written to by `mkstemp` and thus
+  ## can't be a string literal. If in doubt copy the string before passing it.
+
 proc utimes*(path: cstring, times: ptr array[2, Timeval]): int {.
   importc: "utimes", header: "<sys/time.h>".}
   ## Sets file access and modification times.