component/file: support zstd compression

Previously, zstd support was only compiled if zstlib was installed in
the system.

component/file/buildout.cfg

@@ -7,6 +7,7 @@ extends =
   ../bzip2/buildout.cfg
   ../xz-utils/buildout.cfg
   ../zlib/buildout.cfg
+  ../zstd/buildout.cfg
 
 [file]
 recipe = slapos.recipe.cmmi
@@ -19,6 +20,7 @@ configure-options =
   --enable-zlib
   --enable-bzlib
   --enable-xzlib
+  --enable-zstdlib
 environment =
-  CPPFLAGS=-I${bzip2:location}/include -I${xz-utils:location}/include -I${zlib:location}/include
-  LDFLAGS=-L${bzip2:location}/lib -Wl,-rpath=${bzip2:location}/lib -L${xz-utils:location}/lib -Wl,-rpath=${xz-utils:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib
+  CPPFLAGS=-I${bzip2:location}/include -I${xz-utils:location}/include -I${zlib:location}/include -I${zstd:location}/include
+  LDFLAGS=-L${bzip2:location}/lib -Wl,-rpath=${bzip2:location}/lib -L${xz-utils:location}/lib -Wl,-rpath=${xz-utils:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${zstd:location}/lib -Wl,-rpath=${zstd:location}/lib