std.Build: start using the cache system with RunStep

 * Use std.Build.Cache.Directory instead of a string for storing the
   cache roots and build roots.
 * Set up a std.Build.Cache in build_runner.zig and use it in
   std.Build.RunStep for avoiding redundant work.

1 files changed, 3 insertions, 6 deletions

diff --git a/build.zig b/build.zig
index 2e5c3ddd96..e121850221 100644
--- a/build.zig
+++ b/build.zig
@@ -40,11 +40,8 @@ pub fn build(b: *std.Build) !void {
     });
     docgen_exe.single_threaded = single_threaded;
 
-    const rel_zig_exe = try fs.path.relative(b.allocator, b.build_root, b.zig_exe);
-    const langref_out_path = fs.path.join(
-        b.allocator,
-        &[_][]const u8{ b.cache_root, "langref.html" },
-    ) catch unreachable;
+    const rel_zig_exe = try b.build_root.join(b.allocator, &.{b.zig_exe});
+    const langref_out_path = try b.cache_root.join(b.allocator, &.{"langref.html"});
     const docgen_cmd = docgen_exe.run();
     docgen_cmd.addArgs(&[_][]const u8{
         "--zig",
@@ -215,7 +212,7 @@ pub fn build(b: *std.Build) !void {
 
         var code: u8 = undefined;
         const git_describe_untrimmed = b.execAllowFail(&[_][]const u8{
-            "git", "-C", b.build_root, "describe", "--match", "*.*.*", "--tags",
+            "git", "-C", b.build_root.path orelse ".", "describe", "--match", "*.*.*", "--tags",
         }, &code, .Ignore) catch {
             break :v version_string;
         };