Turn arch-native flag off by default

In benchmarks it's own, because if you care about speed, you'll enable
it.

CHANGES.md

@@ -1,5 +1,9 @@
 See also https://pvp.haskell.org/faq
 
+## Version 1.4.7.0
+
+ * Make `arch-native` disabled by default.
+
 ## Version 1.4.6.0
 
  * Use GND&DerivingVia to derive `newtype` intances (`Data.Semigroup`, `Data.Monoid`, `Identity` etc).

hashable.cabal

@@ -1,6 +1,6 @@
 cabal-version: 2.2
 name: hashable
-version: 1.4.6.0
+version: 1.4.7.0
 synopsis: A class for types that can be converted to a hash value
 description:
  This package defines a class, 'Hashable', for types that can be converted to a hash value.
@@ -61,10 +61,11 @@ flag integer-gmp
 flag arch-native
  description:
  Use @-march=native@ when compiling C sources.
- You may need to disable this flag if you are building distributable binaries
+ Portable implementation is 15-50% slower.
+ Consider enabling this flag if hashing performance is important.
 
  manual: True
- default: True
+ default: False
 
 flag random-initial-seed
  description: