package/bash: add /bin/bash to /etc/shells

When bash is selected, /bin/bash is not added to /etc/shells
(see man shells). So, login tools like dropbear reject the ssh
connexions for users using bash as shell in /etc/passwd.

buildroot authpriv.warn dropbear[853]: User 'kubu' has invalid shell, rejected

Reported-by: Jeremy Rosen <jeremy.rosen@smile.fr>
Signed-off-by: Romain Naour <romain.naour@smile.fr>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/bash/bash.mk

@@ -40,10 +40,14 @@ endif
 endif
 
 # Make /bin/sh -> bash (no other shell, better than busybox shells)
+# Add /bin/bash to /etc/shells otherwise some login tools like dropbear
+# can reject the user connexion. See man shells.
 define BASH_INSTALL_TARGET_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D) \
 		DESTDIR=$(TARGET_DIR) exec_prefix=/ install
 	rm -f $(TARGET_DIR)/bin/bashbug
+	grep -qsE '^/bin/bash' $(TARGET_DIR)/etc/shells \
+		|| echo "/bin/bash" >> $(TARGET_DIR)/etc/shells
 endef
 
 $(eval $(autotools-package))