declare linker test bankruptcy

The active contributors and maintainers of Zig's linker code have
generally found the current linker test harness to be cumbersome. The
tests require a lot of maintenance, but do not provide a lot of
coverage, and when they fail it is painful to troubleshoot.

Furthermore, as part of working on #31691, I don't want to port over the
CheckObject step, because I don't like the code anyway.

The plan forward is to start enhancing `zig objdump` to assist in
linker development, as well as using it as the basis for snapshot
testing.

We absolutely need linker test coverage, but we need to try to improve
these things about the next attempt:
* less effort to create and maintain tests
* less CPU overhead - we should be able to add a lot of tests without
  adding a lot of CI time.
* more helpful failures. A failed linker test should provide the next
  steps a developer can take to understand why the test failed.
* a goal of porting over all of LLD's test suite, or at least the good
  ones.

I'm not going to open an issue to track the lost linker test coverage,
because there was already so much lack of coverage for linker stuff.

However I will open issues to track this lost coverage:
* the deleted checks from test/standalone/glibc_compat/build.zig
* the deleted checks from test/standalone/compiler_rt_panic/build.zig
* the deleted checks from test/standalone/ios/build.zig

build.zig

@@ -618,7 +618,6 @@ pub fn build(b: *std.Build) !void {
         .skip_llvm = skip_llvm,
         .max_rss = 3_300_000_000,
     }));
-    test_step.dependOn(tests.addLinkTests(b, enable_macos_sdk, enable_ios_sdk, enable_symlinks_windows));
     test_step.dependOn(tests.addStackTraceTests(b, test_filters, skip_non_native));
     test_step.dependOn(tests.addErrorTraceTests(b, test_filters, optimize_modes, skip_non_native));
     test_step.dependOn(tests.addCliTests(b));