vim: install /bin/vi as a relative symlink

Prevent creating a dangling symlink when vim is not present on the host
machine. With BR2_ROOTFS_MERGED_USR, just link to "vim", since they are
on the same directory, otherwise link to "../usr/bin/vim".

Signed-off-by: Carlos Santos <casantos@datacom.com.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 52385d789af0d17bf12406e5c028651ccbd841f0)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/vim/vim.mk

@@ -65,9 +65,15 @@ define VIM_REMOVE_DOCS
 endef
 
 # Avoid oopses with vipw/vigr, lack of $EDITOR and 'vi' command expectation
+ifeq ($(BR2_ROOTFS_MERGED_USR),y)
 define VIM_INSTALL_VI_SYMLINK
-	ln -sf /usr/bin/vim $(TARGET_DIR)/bin/vi
+	ln -sf vim $(TARGET_DIR)/usr/bin/vi
 endef
+else
+define VIM_INSTALL_VI_SYMLINK
+	ln -sf ../usr/bin/vim $(TARGET_DIR)/bin/vi
+endef
+endif
 VIM_POST_INSTALL_TARGET_HOOKS += VIM_INSTALL_VI_SYMLINK
 
 ifeq ($(BR2_PACKAGE_VIM_RUNTIME),y)