docs: use a single nix-build for all the generate function docs

doc/Makefile

@@ -21,7 +21,7 @@ fix-misc-xml:
 
 .PHONY: clean
 clean:
-	rm -f ${MD_TARGETS} .version manual-full.xml functions/library/locations.xml functions/library/generated
+	rm -f ${MD_TARGETS} doc-support/result .version manual-full.xml functions/library/locations.xml functions/library/generated
 	rm -rf ./out/ ./highlightjs
 
 .PHONY: validate
@@ -78,14 +78,14 @@ manual-full.xml: ${MD_TARGETS} .version functions/library/locations.xml function
 	nix-instantiate --eval \
 		-E '(import ../lib).version' > .version
 
-functions/library/locations.xml:
-	nix-build ./lib-function-locations.nix \
-		--out-link $@
+doc-support/result:
+	(cd doc-support; nix-build)
 
-functions/library/generated: functions/library/locations.xml
-	nix-build ./lib-function-docs.nix \
-		--arg locationsXml $< \
-		--out-link $@
+functions/library/locations.xml: doc-support/result
+	ln -rfs ./doc-support/result/function-locations.xml functions/library/locations.xml
+
+functions/library/generated: doc-support/result
+	ln -rfs ./doc-support/result/function-docs functions/library/generated
 
 %.section.xml: %.section.md
 	pandoc $^ -w docbook+smart \

doc/default.nix

@@ -1,8 +1,7 @@
 { pkgs ? (import ./.. { }), nixpkgs ? { }}:
 let
   lib = pkgs.lib;
-  locationsXml = import ./lib-function-locations.nix { inherit pkgs nixpkgs; };
-  functionDocs = import ./lib-function-docs.nix { inherit locationsXml pkgs; };
+  doc-support = import ./doc-support { inherit pkgs nixpkgs; };
 in pkgs.stdenv.mkDerivation {
   name = "nixpkgs-manual";
 
@@ -30,9 +29,6 @@ in pkgs.stdenv.mkDerivation {
   ];
 
   postPatch = ''
-    rm -rf ./functions/library/locations.xml
-    ln -s ${locationsXml} ./functions/library/locations.xml
-    ln -s ${functionDocs} ./functions/library/generated
     echo ${lib.version} > .version
   '';
 

doc/doc-support/default.nix

@@ -0,0 +1,14 @@
+{ pkgs ? (import ../.. {}), nixpkgs ? { }}:
+let
+  locationsXml = import ./lib-function-locations.nix { inherit pkgs nixpkgs; };
+  functionDocs = import ./lib-function-docs.nix { inherit locationsXml pkgs; };
+in pkgs.runCommand "doc-support" {}
+''
+  mkdir result
+  (
+    cd result
+    ln -s ${locationsXml} ./function-locations.xml
+    ln -s ${functionDocs} ./function-docs
+  )
+  mv result $out
+''

doc/doc-support/lib-function-docs.nix

@@ -6,7 +6,7 @@
 
 with pkgs; stdenv.mkDerivation {
   name = "nixpkgs-lib-docs";
-  src = ./../lib;
+  src = ./../../lib;
 
   buildInputs = [ nixdoc ];
   installPhase = ''