eliminate stderr usage in std.Build make() functions

* Eliminate all uses of `std.debug.print` in make() functions, instead
  properly using the step failure reporting mechanism.
* Introduce the concept of skipped build steps. These do not cause the
  build to fail, and they do allow their dependants to run.
* RunStep gains a new flag, `skip_foreign_checks` which causes the
  RunStep to be skipped if stdio mode is `check` and the binary cannot
  be executed due to it being a foreign executable.
  - RunStep is improved to automatically use known interpreters to
    execute binaries if possible (integrating with flags such as
    -fqemu and -fwasmtime). It only does this after attempting a native
    execution and receiving a "exec file format" error.
  - Update RunStep to use an ArrayList for the checks rather than this
    ad-hoc reallocation/copying mechanism.
  - `expectStdOutEqual` now also implicitly adds an exit_code==0 check
    if there is not already an expected termination. This matches
    previously expected behavior from older API and can be overridden by
    directly setting the checks array.
* Add `dest_sub_path` to `InstallArtifactStep` which allows choosing an
  arbitrary subdirectory relative to the prefix, as well as overriding
  the basename.
  - Delete the custom InstallWithRename step that I found deep in the
    test/ directory.
* WriteFileStep will now update its step display name after the first
  file is added.
* Add missing stdout checks to various standalone test case build
  scripts.

lib/std/child_process.zig

@@ -185,7 +185,6 @@ pub const ChildProcess = struct {
     }
 
     /// Blocks until child process terminates and then cleans up all resources.
-    /// TODO: set the pid to undefined in this function.
     pub fn wait(self: *ChildProcess) !Term {
         const term = if (builtin.os.tag == .windows)
             try self.waitWindows()