add `bb` and `bbsh` shortcuts as aliases to the main shell so we can install
symlinks in Gentoo at /bin/bb as our recovery shell.

we also add fallbacks to /bin/busybox and /bin/busybox.static in case /proc
is not yet mounted during early boot.

rebase the patch to 1.38.0

--- a/shell/ash.c
+++ b/shell/ash.c
@@ -181,6 +181,8 @@
 //                      APPLET_ODDNAME:name  main location    suid_type     help
 //applet:IF_SH_IS_ASH(  APPLET_ODDNAME(sh,   ash, BB_DIR_BIN, BB_SUID_DROP, ash))
 //applet:IF_BASH_IS_ASH(APPLET_ODDNAME(bash, ash, BB_DIR_BIN, BB_SUID_DROP, ash))
+//applet:IF_ASH(APPLET_ODDNAME(bb, ash, BB_DIR_BIN, BB_SUID_DROP, ash))
+//applet:IF_ASH(APPLET_ODDNAME(bbsh, ash, BB_DIR_BIN, BB_SUID_DROP, ash))
 
 //kbuild:lib-$(CONFIG_SHELL_ASH) += ash.o ash_ptr_hack.o shell_common.o
 //kbuild:lib-$(CONFIG_ASH_RANDOM_SUPPORT) += random.o
@@ -6164,6 +6166,8 @@ tryexec_applet(int applet_no, const char *cmd, char **argv, char **envp)
 	}
 	/* re-exec ourselves with the new arguments */
 	execve(bb_busybox_exec_path, argv, envp);
+	execve("/bin/busybox.static", argv, envp);
+	execve("/bin/busybox", argv, envp);
 	/* If they called chroot or otherwise made the binary
 	 * no longer executable, return.
 	 */
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -345,6 +345,8 @@
 //                       APPLET_ODDNAME:name  main  location    suid_type     help
 //applet:IF_SH_IS_HUSH(  APPLET_ODDNAME(sh,   hush, BB_DIR_BIN, BB_SUID_DROP, hush))
 //applet:IF_BASH_IS_HUSH(APPLET_ODDNAME(bash, hush, BB_DIR_BIN, BB_SUID_DROP, hush))
+//applet:IF_HUSH(APPLET_ODDNAME(bb, hush, BB_DIR_BIN, BB_SUID_DROP, hush))
+//applet:IF_HUSH(APPLET_ODDNAME(bbsh, hush, BB_DIR_BIN, BB_SUID_DROP, hush))
 
 //kbuild:lib-$(CONFIG_SHELL_HUSH) += hush.o match.o shell_common.o
 //kbuild:lib-$(CONFIG_HUSH_RANDOM_SUPPORT) += random.o
@@ -8104,6 +8106,8 @@ static NORETURN void re_execute_shell(
 	if (SPECIAL_JOBSTOP_SIGS != 0)
 		switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
 	execve(bb_busybox_exec_path, argv, pp);
+	execve("/bin/busybox.static", argv, pp);
+	execve("/bin/busybox", argv, pp);
 	/* Fallback. Useful for init=/bin/hush usage etc */
 	if (argv[0][0] == '/')
 		execve(argv[0], argv, pp);
@@ -9397,6 +9401,8 @@ static NORETURN NOINLINE void pseudo_exec_argv(
 			if (SPECIAL_JOBSTOP_SIGS != 0)
 				switch_off_special_sigs(G.special_sig_mask & SPECIAL_JOBSTOP_SIGS);
 			execv(bb_busybox_exec_path, argv);
+			execv("/bin/busybox.static", argv);
+			execv("/bin/busybox", argv);
 			/* If they called chroot or otherwise made the binary no longer
 			 * executable, fall through */
 		}