[lld] Fix test crashing when AVR target is missing

Fixes buildbot error.

GitOrigin-RevId: 7c6f17747760ccc61c395a16ecc268ac311d735a
diff --git a/test/ELF/avr-flags.s b/test/ELF/avr-flags.s
index 61e86ba..69e08cd 100644
--- a/test/ELF/avr-flags.s
+++ b/test/ELF/avr-flags.s
@@ -1,3 +1,5 @@
+; REQUIRES: avr
+
 ; RUN: llvm-mc -filetype=obj -triple=avr -mcpu=avr5 %s -o %t-v5
 ; RUN: llvm-mc -filetype=obj -triple=avr -mcpu=avrxmega3 %s -o %t-xmega3
 ; RUN: ld.lld %t-v5 -o %t-v5.out