Fix arithmetic expression exit status in test-all.sh (#121) (#122)

Replace ((TESTED++)) with TESTED=$((TESTED + 1)) to avoid returning
exit status 1 when TESTED is 0. The post-increment expression evaluates
to 0, which bash treats as false, causing issues with set -e and
incorrect exit status reporting in IDE terminals.

Author: lex57ukr

tests/deb/test-all.sh

@@ -107,7 +107,7 @@ for target in "${BUILD_TARGETS[@]}"; do
 
         if ./tests/deb/test-package.sh "$deb_file" "$image"; then
             echo "PASSED: $rid on $image"
-            ((TESTED++))
+            TESTED=$((TESTED + 1))
         else
             echo "FAILED: $rid on $image"
             FAILED=1