squisher: use 1024mb to sign

512 seems to error out on certain builds

Change-Id: I5e20d7101c26fabd488f4bc21e589609a3faef63
Signed-off-by: Roman Birg <romanbirg@gmail.com>

tools/squisher

@@ -152,7 +152,7 @@ printf "Zipping package..."
 echo
 printf "Signing package..."
 SECURITYDIR=$ANDROID_BUILD_TOP/build/target/product/security
-java -Xmx512m \
+java -Xmx1024m \
 	-jar $ANDROID_BUILD_TOP/out/host/$OUT_TARGET_HOST/framework/signapk.jar \
 	-w $SECURITYDIR/testkey.x509.pem $SECURITYDIR/testkey.pk8 \
 	$REPACK/update.zip $OUTFILE