shaderir/glsl: Bug fix: Calculate local variable indices correctly

Fixes #1339

internal/shader/testdata/array2.expected.vs

@@ -0,0 +1,22 @@
+void F0(out vec2 l0[3]);
+
+void F0(out vec2 l0[3]) {
+	vec2 l1[2];
+	l1[0] = vec2(0);
+	l1[1] = vec2(0);
+	vec2 l2[3];
+	l2[0] = vec2(0);
+	l2[1] = vec2(0);
+	l2[2] = vec2(0);
+	{
+		vec2 l2[2];
+		l2[0] = vec2(0);
+		l2[1] = vec2(0);
+		l2[0] = l1[0];
+		l2[1] = l1[1];
+	}
+	l0[0] = l2[0];
+	l0[1] = l2[1];
+	l0[2] = l2[2];
+	return;
+}

internal/shader/testdata/array2.go

@@ -0,0 +1,11 @@
+package main
+
+func Foo() [3]vec2 {
+	var a [2]vec2
+	{
+		var b [2]vec2
+		b = a
+	}
+	var c [3]vec2
+	return c
+}

internal/shaderir/glsl/glsl.go

@@ -282,7 +282,8 @@ func descendantLocalVars(block, target *shaderir.Block) ([]shaderir.Type, bool)
 	for _, s := range block.Stmts {
 		for _, b := range s.Blocks {
 			if ts2, found := descendantLocalVars(b, target); found {
-				ts = append(ts, block.LocalVars...)
+				n := b.LocalVarIndexOffset - block.LocalVarIndexOffset
+				ts = append(ts, block.LocalVars[:n]...)
 				ts = append(ts, ts2...)
 				return ts, true
 			}