Allow assert disable (#2168)

* Add +verilator+noassert flag

This allows to disable the assert check per simulation argument.

* Add AssertOn check for assert

Insert the check AssertOn to allow disabling of asserts.
Asserts can be disabled by not using the `--assert` flag or by calling
`AssertOn(false)`, or passing the "+verilator+noassert" runtime flag.
Add tests for this behavior.
Bad tests check that the assert still causes a stop.
Non bad tests check that asserts are properly disabled and cause no stop
of the simulation.

Fixes #2162.

Signed-off-by: Tobias Wölfel <[email protected]>

* Correct file location

Signed-off-by: Tobias Wölfel <[email protected]>

* Add description for single test execution

Without this description it is not obvious how to run a single test from
the regression test suite.

Signed-off-by: Tobias Wölfel <[email protected]>

include/verilated.cpp

@@ -2199,6 +2199,9 @@ void VerilatedImp::commandArgVl(const std::string& arg) {
         else if (commandArgVlValue(arg, "+verilator+seed+", value/*ref*/)) {
             Verilated::randSeed(atoi(value.c_str()));
         }
+        else if (arg == "+verilator+noassert") {
+            Verilated::assertOn(false);
+        }
         else if (arg == "+verilator+V") {
             versionDump();  // Someday more info too
             VL_FATAL_MT("COMMAND_LINE", 0, "",