cmd/compile: terminate compilation if type-checking fails

There is no benefit in continuing compilation if there
are type-checking errors. This will increase robustness
of the compiler in the presence of errors.

Fixes #22909.

Change-Id: I1c70c667e5927646ba3d0f370e33705165620f12
Reviewed-on: https://go-review.googlesource.com/116335
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/gc/main.go

@@ -532,6 +532,10 @@ func Main(archInit func(*Arch)) {
 	checkMapKeys()
 	timings.AddEvent(fcount, "funcs")
 
+	if nsavederrors+nerrors != 0 {
+		errorexit()
+	}
+
 	// Phase 4: Decide how to capture closed variables.
 	// This needs to run before escape analysis,
 	// because variables captured by value do not escape.