docs: Refer to the glossary with @docroot@ instead of ..

These unweildy relative paths probably predate the `@docroot@`
mechanism.

doc/manual/src/command-ref/nix-build.md

@@ -41,7 +41,7 @@ expression to a low-level [store derivation]) and [`nix-store
 --realise`](@docroot@/command-ref/nix-store/realise.md) (to build the store
 derivation).
 
-[store derivation]: ../glossary.md#gloss-store-derivation
+[store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
 > **Warning**
 >

doc/manual/src/command-ref/nix-copy-closure.md

@@ -49,7 +49,7 @@ authentication, you can avoid typing the passphrase with `ssh-agent`.
   - `--include-outputs`\
     Also copy the outputs of [store derivation]s included in the closure.
 
-    [store derivation]: ../glossary.md#gloss-store-derivation
+    [store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
   - `--use-substitutes` / `-s`\
     Attempt to download missing paths on the target machine using Nix’s

doc/manual/src/command-ref/nix-instantiate.md

@@ -23,7 +23,7 @@ It evaluates the Nix expressions in each of *files* (which defaults to
 derivation, a list of derivations, or a set of derivations. The paths
 of the resulting store derivations are printed on standard output.
 
-[store derivation]: ../glossary.md#gloss-store-derivation
+[store derivation]: @docroot@/glossary.md#gloss-store-derivation
 
 If *files* is the character `-`, then a Nix expression will be read from
 standard input.

doc/manual/src/command-ref/nix-store/query.md

@@ -40,12 +40,12 @@ symlink.
     derivations *paths*. These are the paths that will be produced when
     the derivation is built.
 
-    [output paths]: ../../glossary.md#gloss-output-path
+    [output paths]: @docroot@/glossary.md#gloss-output-path
 
   - `--requisites`; `-R`\
     Prints out the [closure] of the store path *paths*.
 
-    [closure]: ../../glossary.md#gloss-closure
+    [closure]: @docroot@/glossary.md#gloss-closure
 
     This query has one option:
 
@@ -66,7 +66,7 @@ symlink.
     *paths*, that is, their immediate dependencies. (For *all*
     dependencies, use `--requisites`.)
 
-    [references]: ../../glossary.md#gloss-reference
+    [references]: @docroot@/glossary.md#gloss-reference
 
   - `--referrers`\
     Prints the set of *referrers* of the store paths *paths*, that is,
@@ -90,7 +90,7 @@ symlink.
     example when *paths* were substituted from a binary cache.
     Use `--valid-derivers` instead to obtain valid paths only.
 
-    [deriver]: ../../glossary.md#gloss-deriver
+    [deriver]: @docroot@/glossary.md#gloss-deriver
 
   - `--valid-derivers`\
     Prints a set of derivation files (`.drv`) which are supposed produce