Add docs

Cabal/doc/installing-packages.rst

@@ -1135,6 +1135,16 @@ Miscellaneous options
 
     (default) Do not build shared library.
 
+.. option:: --enable-static
+
+   Build a static library. This passes ``-staticlib`` to GHC (avaiable
+   for iOS, and with 8.4 more platforms).  The result is an archive ``.a``
+   containing all dependent haskell libararies combined.
+
+.. option:: --disable-static
+
+    (default) Do not build a static library.
+
 .. option:: --enable-executable-dynamic
 
     Link executables dynamically. The executable's library dependencies

Cabal/doc/nix-local-build.rst

@@ -1205,6 +1205,21 @@ Dynamic linking options
 
     The command line variant of this flag is ``--relocatable``.
 
+Static linking options
+^^^^^^^^^^^^^^^^^^^^^^
+
+.. cfg-field:: static: boolean
+               --enable-static
+               --disable-static
+    :synopsis: Build static library.
+
+
+    :default: False
+
+    Roll this and all dependent libraries into a combined ``.a`` archive.
+    This uses GHCs ``-staticlib`` flag, which is avaiable for iOS and with
+    GHC 8.4 and later for other platforms as well.
+
 Foreign function interface options
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^