hadrian: Refactor file patterns for future Shake changes (fixes #17005)

Shake will be moving from its current implementation of ?== to one from
System.FilePattern. Support for `//` is being dropped, leaving only `*`
and `**` as special forms. This commit converts the existing file
patterns in Hadrian to the new format. It also removes all occurances
of <//> and changes the user-settings docs to remove references to //
and add **.

The conversion is as follows:

- //a ==> **/a

- a// ==> a/**

- a//b ==> a/**/b

1 files changed, 3 insertions, 3 deletions

diff --git a/hadrian/src/Main.hs b/hadrian/src/Main.hs
index 3692047317..7e8c593453 100644
--- a/hadrian/src/Main.hs
+++ b/hadrian/src/Main.hs
@@ -29,7 +29,7 @@ main = do
 
         BuildRoot buildRoot = CommandLine.lookupBuildRoot argsMap
 
-        rebuild = [ (RebuildLater, buildRoot -/- "stage0//*")
+        rebuild = [ (RebuildLater, buildRoot -/- "stage0/**")
                   | CommandLine.lookupFreeze1 argsMap ]
 
     cwd <- getCurrentDirectory
@@ -60,11 +60,11 @@ main = do
             , shakeLintIgnore =
                 -- Ignore access to the package database caches.
                 -- They are managed externally by the ghc-pkg tool.
-                [ buildRoot -/- "//package.conf.d/package.cache"
+                [ buildRoot -/- "**/package.conf.d/package.cache"
 
                 -- Ignore access to autom4te.cache directories.
                 -- They are managed externally by auto tools.
-                , "//autom4te.cache//*"
+                , "**/autom4te.cache/**"
                 ]
             }