make busybox --install work even if /proc/self/exe doesn't exist

# size busybox_old busybox_unstripped
   text    data     bss     dec     hex filename
 680095    2704   15648  698447   aa84f busybox_old
 680099    2704   15648  698451   aa853 busybox_unstripped

3 files changed, 5 insertions, 4 deletions

diff --git a/libbb/execable.c b/libbb/execable.c
index d84364753..f679108be 100644
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -65,7 +65,7 @@ int exists_execable(const char *filename)
  */
 int bb_execvp(const char *file, char *const argv[])
 {
-        return execvp(find_applet_by_name(file) ? CONFIG_BUSYBOX_EXEC_PATH : file,
+        return execvp(find_applet_by_name(file) ? bb_busybox_exec_path : file,
                                         argv);
 }
 #endif
diff --git a/libbb/messages.c b/libbb/messages.c
index fbd882c43..16aaea553 100644
--- a/libbb/messages.c
+++ b/libbb/messages.c
@@ -37,8 +37,9 @@ const char bb_path_gshadow_file[] = "/etc/gshadow";
 const char bb_path_nologin_file[] = "/etc/nologin";
 const char bb_path_securetty_file[] = "/etc/securetty";
 const char bb_path_motd_file[] = "/etc/motd";
-const char bb_default_login_shell[] = LIBBB_DEFAULT_LOGIN_SHELL;
 const char bb_dev_null[] = "/dev/null";
+const char bb_busybox_exec_path[] = CONFIG_BUSYBOX_EXEC_PATH;
+const char bb_default_login_shell[] = LIBBB_DEFAULT_LOGIN_SHELL;
 
 const int const_int_0;
 const int const_int_1 = 1;
diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c
index 349628796..cb4dee799 100644
--- a/libbb/vfork_daemon_rexec.c
+++ b/libbb/vfork_daemon_rexec.c
@@ -220,8 +220,8 @@ void forkexit_or_rexec(char **argv)
         /* high-order bit of first char in argv[0] is a hidden
          * "we have (alrealy) re-execed, don't do it again" flag */
         argv[0][0] |= 0x80;
-        execv(CONFIG_BUSYBOX_EXEC_PATH, argv);
-        bb_perror_msg_and_die("exec %s", CONFIG_BUSYBOX_EXEC_PATH);
+        execv(bb_busybox_exec_path, argv);
+        bb_perror_msg_and_die("exec %s", bb_busybox_exec_path);
 }
 #else
 /* Dance around (void)...*/