Configure test fixture using CTest for Windows build

- Added new test/test_suite.in with list of regression and unit tests
  previously in Makefile.am, to be shared between Unix and Windows
  builds.
- Updated regression.cc & unit.cc to return the number of failed tests
  to indicate to CTest that the test failed. Similarly, a crash or
  unhandled exception terminates the process with a non-zero exit code.
  - This change doesn't affect running the tests with autotest in Unix
    builds because this processes test output from custom-test-driver &
    test-suite.sh, and ignores the exit code of the test runner.
- Removed comment in test/test-cases/regression-offset-variable.json as
  this is not supported by JSON and prevents strict parsers to read and
  process the file.
- Minor change in regression.cc's clearAuditLog to replace std::ifstream
  with std::ofstream as the mode to open the flag applies to an output
  stream.
- Minor change in unit.cc to simplify code that deletes tests.
- Minor changes to test/custom-test-driver to correct usage information.

test/regression/regression.cc

@@ -64,13 +64,11 @@ bool contains(const std::string &s, const std::string &pattern) {
 
 void clearAuditLog(const std::string &filename) {
     if (!filename.empty()) {
-        std::ifstream file;
-        file.open(filename.c_str(), std::ifstream::out | std::ifstream::trunc);
+        std::ofstream file{filename.c_str(), std::ofstream::out | std::ofstream::trunc};
         if (!file.is_open() || file.fail()) {
             std::cout << std::endl << "Failed to clear previous contents of audit log: " \
                 << filename << std::endl;
         }
-        file.close();
     }
 }
 std::string getAuditLogContent(const std::string &filename) {
@@ -510,6 +508,7 @@ int main(int argc, char **argv) {
 #ifdef NO_LOGS
     std::cout << "Test utility cannot work without logging support." \
         << std::endl;
+    return 0;
 #else
     test.cmd_options(argc, argv);
     if (!test.m_automake_output && !test.m_count_all) {
@@ -609,6 +608,6 @@ int main(int argc, char **argv) {
         delete vec;
     }
 
+    return failed;
 #endif
-    return 0;
 }