[EXPERIMENT] Test 8-bit tags for hashbrown

See rust-lang/hashbrown#653

Author: Amanieu

library/std/Cargo.toml

@@ -20,7 +20,7 @@ panic_unwind = { path = "../panic_unwind", optional = true }
 panic_abort = { path = "../panic_abort" }
 core = { path = "../core", public = true }
 unwind = { path = "../unwind" }
-hashbrown = { version = "0.15", default-features = false, features = [
+hashbrown = { git = "https://github.com/gaujay/hashbrown.git", branch = "8-bits-tag", default-features = false, features = [
     'rustc-dep-of-std',
 ] }
 std_detect = { path = "../std_detect", public = true }