Add GHC boot package to glossary

Author: mpilgrem

doc/build_command.md

@@ -85,12 +85,12 @@ supported syntaxes for targets are:
     of the test suite and benchmark components, respectively, are selected to be
     built.
 
-    Stackage snapshots do not include directly the packages in GHC's global
-    package database which come with GHC (GHC boot libraries). For example, if
-    `Cabal` is not a local package or an extra dep, then `stack build Cabal`
-    will specify the latest version of that package in the package index, which
-    may differ from the version provided by the version of GHC specified by the
-    snapshot.
+    Stackage snapshots do not include directly GHC boot packages (packages that
+    come with GHC and are included in GHC's global package database). For
+    example, if `Cabal` is not a local package or an extra dep, then
+    `stack build Cabal` will specify the latest version of that package in the
+    package index, which may differ from the version provided by the version of
+    GHC specified by the snapshot.
 
 *   *package identifier*, e.g. `stack build foobar-1.2.3`, is usually used to
     include specific package versions from the package index. If the version

doc/glossary.md

@@ -18,6 +18,7 @@ The following terms are used in Stack's documentation.
 |FreeBSD            |A Unix-like operating system.                             |
 |GCC                |The [GNU Compiler Collection](https://gcc.gnu.org/) or its executable `gcc`.|
 |GHC                |The [Glasgow Haskell Compiler](https://www.haskell.org/ghc/).|
+|GHC boot package   |A package that comes with GHC, is included in GHC's global package database, and is not included in a Stackage snapshot. See the output of command `stack exec -- ghc-pkg list --global`.|
 |GHCi               |GHC's [interactive environment](https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html).|
 |GHCJS              |A Haskell to JavaScript [compiler](https://github.com/ghcjs/ghcjs).|
 |GHCup              |An [installer](https://www.haskell.org/ghcup/) for Haskell.