ash: optimise running of scripts (2)

Commit 4b7b4a960 (ash: optimise running of scripts) avoided creation
of a process when running a script.  There's another case where we
can do the same:  if the script is being run from a FS_SHELLEXEC
shell.

- Check the necessary conditions for this to happen.

- Allocate two extra slots in the argv array for FS_SHELLEXEC.

- Set the index of the script file in the argv array.  Without this
  the test 'pidof this' failed because the command name hadn't been
  correctly set.

Adds 80-96 bytes.

1 files changed, 1 insertions, 0 deletions

diff --git a/include/mingw.h b/include/mingw.h
index ed7884e39..65940b40b 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -667,3 +667,4 @@ enum {
         ADMIN_ENABLED = 2
 };
 int elevation_state(void);
+void set_interp(int i) FAST_FUNC;