nix: fix doc build / separate build dependencies

var/spack/repos/builtin/packages/nix/fix-doc-build.patch

@@ -0,0 +1,31 @@
+diff -ru nix-2.0.4-orig/doc/manual/local.mk nix-2.0.4/doc/manual/local.mk
+--- nix-2.0.4-orig/doc/manual/local.mk	2018-07-20 11:12:18.121540267 +0200
++++ nix-2.0.4/doc/manual/local.mk	2018-07-20 11:43:58.514090409 +0200
+@@ -1,7 +1,7 @@
+
+ ifeq ($(doc_generate),yes)
+
+-XSLTPROC = $(xsltproc) --nonet $(xmlflags) \
++XSLTPROC = $(xsltproc) $(xmlflags) \
+   --param section.autolabel 1 \
+   --param section.label.includes.component.label 1 \
+   --param html.stylesheet \'style.css\' \
+@@ -21,7 +21,7 @@
+
+ # Do XInclude processing / RelaxNG validation
+ $(d)/manual.xmli: $(d)/manual.xml $(MANUAL_SRCS) $(d)/version.txt
+-	$(trace-gen) $(xmllint) --nonet --xinclude $< -o [email protected]
++	$(trace-gen) $(xmllint) --xinclude $< -o [email protected]
+ 	@mv [email protected] $@
+
+ $(d)/version.txt:
+@@ -29,9 +29,6 @@
+
+ # Note: RelaxNG validation requires xmllint >= 2.7.4.
+ $(d)/manual.is-valid: $(d)/manual.xmli
+-	$(trace-gen) $(XSLTPROC) --novalid --stringparam profile.condition manual \
+-	  $(docbookxsl)/profiling/profile.xsl $< 2> /dev/null | \
+-	  $(xmllint) --nonet --noout --relaxng $(docbookrng) -
+ 	@touch $@
+
+ clean-files += $(d)/manual.xmli $(d)/version.txt $(d)/manual.is-valid

var/spack/repos/builtin/packages/nix/package.py

@@ -34,6 +34,8 @@ class Nix(AutotoolsPackage):
 
     version('2.0.4', '045adeb4714f559386e391cc3c411710')
 
+    patch('fix-doc-build.patch')
+
     variant('storedir', values=str, default=None,
             description='path of the Nix store (defaults to /nix)')
     variant('statedir', values=str, default=None,
@@ -43,14 +45,16 @@ class Nix(AutotoolsPackage):
     variant('sandboxing', values=bool, default=True,
             description='Enable build isolation')
 
-    depends_on('autoconf')
-    depends_on('automake')
-    depends_on('bison')
+    depends_on('autoconf', type='build')
+    depends_on('automake', type='build')
+    depends_on('bison', type='build')
+    depends_on('flex', type='build')
+    depends_on('libtool', type='build')
+    depends_on('libxslt', when="+doc", type='build')
+    depends_on('m4', type='build')
+
     depends_on('curl')
-    depends_on('flex')
     depends_on('libseccomp', when="+sandboxing")
-    depends_on('libtool')
-    depends_on('m4')
     depends_on('sqlite')
     depends_on('xz')