loader: separate lang init from scripting init

Create interp_preinit() to initialize the scripting language to run
scripts. Make sure you can call it multiple times, but only the first
one has effect, After it's call, you can run scripts in the scripting
language. At the moment, no functional change.

Sponsored by:		Netflix

stand/common/bootstrap.h

@@ -54,7 +54,8 @@ bool	interp_has_builtin_cmd(const char *cmd);
 
 /* Called by interp.c for interp_*.c embedded interpreters */
 int	interp_include(const char *);	/* Execute commands from filename */
-void	interp_init(void);		/* Initialize interpreater */
+void	interp_preinit(void);		/* Initialize interpreater execution engine */
+void	interp_init(void);		/* Initialize interpreater and run main script */
 int	interp_run(const char *);	/* Run a single command */
 
 /* interp_backslash.c */

stand/common/interp.c

@@ -60,6 +60,7 @@ interact(void)
 	 * we need to switch interpreters.
 	 */
 	interp_identifier = bootprog_interp;
+	interp_preinit();
 	interp_init();
 
 	printf("\n");

stand/common/interp_forth.c

@@ -337,12 +337,21 @@ bf_run(const char *line)
 	return (result);
 }
 
+static bool preinit_run = false;
+
+void
+interp_preinit(void)
+{
+	if (preinit_run)
+		return;
+	setenv("script.lang", "forth", 1);
+	bf_init();
+	preinit_run = true;
+}
+
 void
 interp_init(void)
 {
-
-	setenv("script.lang", "forth", 1);
-	bf_init();
 	/* Read our default configuration. */
 	interp_include("/boot/loader.rc");
 }

stand/common/interp_lua.c

@@ -96,17 +96,21 @@ static const luaL_Reg loadedlibs[] = {
   {NULL, NULL}
 };
 
+static bool preinit_done = false;
+
 void
-interp_init(void)
+interp_preinit(void)
 {
 	lua_State *luap;
 	struct interp_lua_softc	*softc = &lua_softc;
-	const char *filename;
 	const luaL_Reg *lib;
 	lua_init_md_t **fnpp;
 
 	TSENTER();
 
+	if (preinit_done)
+		return;
+
 	setenv("script.lang", "lua", 1);
 	LDBG("creating context");
 
@@ -126,6 +130,21 @@ interp_init(void)
 	LUA_FOREACH_SET(fnpp)
 	    (*fnpp)(luap);
 
+	preinit_done = true;
+
+	TSEXIT();
+}
+
+void
+interp_init(void)
+{
+	lua_State *luap;
+	struct interp_lua_softc	*softc = &lua_softc;
+	const char *filename;
+
+	TSENTER();
+
+	luap = softc->luap;
 	filename = getenv("loader_lua");
 	if (filename == NULL)
 		filename = LOADER_LUA;

stand/common/interp_simple.c

@@ -34,6 +34,11 @@
 
 INTERP_DEFINE("simp");
 
+void
+interp_preinit(void)
+{
+}
+
 void
 interp_init(void)
 {