Remove TODO and stop forcing LLVM usage (again)

Signed-off-by: AnErrupTion <anerruption@disroot.org>

build.zig

@@ -69,7 +69,6 @@ pub fn build(b: *std.Build) !void {
             .optimize = optimize,
             .link_libc = true,
         }),
-        .use_llvm = true,
     });
 
     const ly_ui = b.dependency("ly_ui", .{

ly-core/src/interop.zig

@@ -235,7 +235,6 @@ fn PlatformStruct() type {
 
 const platform_struct = PlatformStruct();
 
-// TODO 0.16.0: Can we get away with this?
 pub fn isError(result: anytype) bool {
     if (@typeInfo(@TypeOf(result)).int.signedness == .signed) {
         return result < 0;