behavior: disable tests triggering LLVM 15 bug

This bug is newly triggered by these tests since some values are now
correctly promoted to comptime-known constants.

Tracked by ziglang#13782

Author: mlugg

test/behavior/vector.zig

@@ -14,6 +14,11 @@ test "implicit cast vector to array - bool" {
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
 
+    if (builtin.zig_backend == .stage2_llvm and builtin.cpu.arch.endian() == .Big) {
+        // https://github.com/ziglang/zig/issues/13782
+        return error.SkipZigTest;
+    }
+
     const S = struct {
         fn doTheTest() !void {
             const a: @Vector(4, bool) = [_]bool{ true, false, true, false };
@@ -492,6 +497,11 @@ test "vector comparison operators" {
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
 
+    if (builtin.zig_backend == .stage2_llvm and builtin.cpu.arch.endian() == .Big) {
+        // https://github.com/ziglang/zig/issues/13782
+        return error.SkipZigTest;
+    }
+
     const S = struct {
         fn doTheTest() !void {
             {