fix another posix thing

Author: SaicharanKandukuri

udroid/src/udroid.sh

@@ -114,7 +114,7 @@ verify_integrity() {
     LOG "filesum=$filesha"
     LOG "shasum=$shasum"
 
-    if [ $filesha -eq $shasum ]; then
+    if [[ $filesha -eq $shasum ]]; then
         LOG "file integrity check failed"
         GWARN "file integrity check failed"
         return 1