Exclude file lib from gems API

The 'file' library makes the gems API depend on the libc, which is not
desireable because most users of the gems API have no direct libc
dependency.

With the changes of issue #4599, the build of each src archive that
depends on the gems API would attempt to build the 'file' library and
thereby demand the libc.

Note that the 'file' library is a relic that should better not be
promoted as part of the gems API. Hence, this patch removes the file
library from the gems API and adds it to the src archives of the few
remaining users.

Issue #4599

repos/gems/recipes/api/gems/content.mk

@@ -1,6 +1,6 @@
-content: include/gems src/lib/file lib/mk/file.mk LICENSE
+content: include/gems LICENSE
 
-include/gems src/lib/file lib/mk/file.mk:
+include/gems:
 	$(mirror_from_rep_dir)
 
 LICENSE:

repos/gems/recipes/src/backdrop/content.mk

@@ -1,2 +1,7 @@
 SRC_DIR := src/app/backdrop
 include $(GENODE_DIR)/repos/base/recipes/src/content.inc
+
+content: src/lib/file lib/mk/file.mk
+
+src/lib/file lib/mk/file.mk:
+	$(mirror_from_rep_dir)

repos/gems/recipes/src/menu_view/content.mk

@@ -6,3 +6,8 @@ content: include/polygon_gfx
 include/polygon_gfx:
 	mkdir -p $@
 	cp $(GENODE_DIR)/repos/gems/include/polygon_gfx/* $@
+
+content: src/lib/file lib/mk/file.mk
+
+src/lib/file lib/mk/file.mk:
+	$(mirror_from_rep_dir)

repos/gems/recipes/src/themed_decorator/content.mk

@@ -6,3 +6,8 @@ content: include/decorator
 include/decorator:
 	mkdir -p $@
 	cp $(GENODE_DIR)/repos/os/include/decorator/* $@
+
+content: src/lib/file lib/mk/file.mk
+
+src/lib/file lib/mk/file.mk:
+	$(mirror_from_rep_dir)