runuser: new applet

Add a cut down, Windows-specific implementation of `runuser` from
util-linux.

This allows elevated privileges to be dropped when running in an
SSH session.  It also works when using `su` or starting busybox-w32
'as administrator'.

There are complications:

- The method used to drop privileges leaves the access token in the
  TokenIsElevated state.  Detecting this is likely to be fragile.

- The unprivileged shell is started by CreateProcessAsUserA().  In
  older versions of Windows this has to be loaded dynamically.

Adds about 900 bytes.

(GitHub issue #240)

1 files changed, 1 insertions, 1 deletions

diff --git a/win32/process.c b/win32/process.c
index d78041251..0585f66a6 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -113,7 +113,7 @@ parse_interpreter(const char *cmd, interp_t *interp)
  * See https://docs.microsoft.com/en-us/cpp/cpp/main-function-command-line-args?view=vs-2019#parsing-c-command-line-arguments
  * (Parsing C++ Command-Line Arguments)
  */
-static char *
+char *
 quote_arg(const char *arg)
 {
         int len = 0, n = 0;