stage2: implement zig build

As part of this:

 * add std.process.cleanExit. closes #6395
   - use it in several places
 * adjust the alignment of text in `zig build --help` menu
 * Cache: support the concept of "unhit" so that we properly keep track
   of the cache when we find out using the secondary hash that the cache
   "hit" was actually a miss. Use this to fix false negatives of caching
   of stage1 build artifacts.
 * fix not deleting the symlink hash for stage1 build artifacts causing
   false positives.
 * implement support for Package arguments in stage1 build artifacts
 * update and add missing usage text
 * add --override-lib-dir and --enable-cache CLI options
   - `--enable-cache` takes the place of `--cache on`
 * CLI supports -femit-bin=foo combined with --enable-cache to do an
   "update file" operation. --enable-cache without that argument
   will build the output into a cache directory and then print the path
   to stdout (matching master branch behavior).
 * errors surfacing from main() now print "error: Foo" instead of
   "error: error.Foo".

1 files changed, 6 insertions, 6 deletions

diff --git a/lib/std/special/build_runner.zig b/lib/std/special/build_runner.zig
index 3c4916a566..43d6b96536 100644
--- a/lib/std/special/build_runner.zig
+++ b/lib/std/special/build_runner.zig
@@ -161,16 +161,16 @@ fn usage(builder: *Builder, already_ran_build: bool, out_stream: anytype) !void
             try fmt.allocPrint(allocator, "{} (default)", .{top_level_step.step.name})
         else
             top_level_step.step.name;
-        try out_stream.print("  {s:22} {}\n", .{ name, top_level_step.description });
+        try out_stream.print("  {s:<27} {}\n", .{ name, top_level_step.description });
     }
 
     try out_stream.writeAll(
         \\
         \\General Options:
-        \\  --help                 Print this help and exit
-        \\  --verbose              Print commands before executing them
-        \\  --prefix [path]        Override default install prefix
-        \\  --search-prefix [path] Add a path to look for binaries, libraries, headers
+        \\  --help                      Print this help and exit
+        \\  --verbose                   Print commands before executing them
+        \\  --prefix [path]             Override default install prefix
+        \\  --search-prefix [path]      Add a path to look for binaries, libraries, headers
         \\
         \\Project-Specific Options:
         \\
@@ -185,7 +185,7 @@ fn usage(builder: *Builder, already_ran_build: bool, out_stream: anytype) !void
                 Builder.typeIdName(option.type_id),
             });
             defer allocator.free(name);
-            try out_stream.print("{s:32} {}\n", .{ name, option.description });
+            try out_stream.print("{s:<29} {}\n", .{ name, option.description });
         }
     }