cmd/compile/internal/ssa: restrict architectures for TestDebugLines_74576

CL 687815 recently added TestDebugLines_74576.

The pre-existing debug_lines_test.go file generally restricts the
tested architectures and contains multiple warnings that the
testing approach is useful but fragile, such as:

  "These files must all be short because this is super-fragile."

Despite that, initially I wanted to see what happened on the
different architectures on the trybots in case it might show something
surprising, and I let TestDebugLines_74576 run on all architectures.

That seemed to initially work, but the test is now failing on a
linux/risc64 builder (#74669), so it is likely more prudent to be
more conservative and restrict the platforms like many of the
other pre-existing tests, which is what this CL now does.

Fixes #74669

Change-Id: I9e5a7d3ee901f58253cf72e03c2239df338479e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/688856
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/debug_lines_test.go

@@ -116,6 +116,15 @@ func TestDebugLines_53456(t *testing.T) {
 }
 
 func TestDebugLines_74576(t *testing.T) {
+	unixOnly(t)
+
+	switch testGoArch() {
+	default:
+		// Failed on linux/riscv64 (issue 74669), but conservatively
+		// skip many architectures like several other tests here.
+		t.Skip("skipped for many architectures")
+
+	case "arm64", "amd64", "loong64":
 		tests := []struct {
 			file      string
 			wantStmts []int
@@ -132,6 +141,7 @@ func TestDebugLines_74576(t *testing.T) {
 			})
 		}
 	}
+}
 
 func compileAndDump(t *testing.T, file, function, moreGCFlags string) []byte {
 	testenv.MustHaveGoBuild(t)