Rollup merge of rust-lang#31992 - brson:bump, r=steveklabnik

Author: steveklabnik

mk/main.mk

@@ -13,7 +13,7 @@
 ######################################################################
 
 # The version number
-CFG_RELEASE_NUM=1.8.0
+CFG_RELEASE_NUM=1.9.0
 
 # An optional number to put after the label, e.g. '.2' -> '-beta.2'
 # NB Make sure it starts with a dot to conform to semver pre-release