rebuild_env: Avoid setting SHELL twice for "sudo -i"

Make sure DID_SHELL is set when we set SHELL in the "sudo -i" case.
Otherwise, it will be set again when setting fallback values.
Reported by Alejandro López at Red Hat.

The code to make sure that SHELL is setu

Author: millert

plugins/sudoers/env.c

@@ -966,6 +966,7 @@ rebuild_env(const struct sudoers_context *ctx)
 	if (ISSET(ctx->mode, MODE_LOGIN_SHELL)) {
 	    CHECK_SETENV2("SHELL", ctx->runas.pw->pw_shell,
 		ISSET(didvar, DID_SHELL), true);
+	    SET(didvar, DID_SHELL);
 #ifdef _AIX
 	    CHECK_SETENV2("LOGIN", ctx->runas.pw->pw_name,
 		ISSET(didvar, DID_LOGIN), true);