gnu: Fix builds that require old blueprint-compiler.

This is a follow-up commit to cee21ef865 and
fixes two builds that rely on an older version of blueprint-compiler.
The giara package remains broken as a result of a test failure.

* gnu/packages/gnome.scm (blueprint-compiler-0.4): New variable.
* gnu/packages/syndication.scm (giara, gfeeds): Replace blueprint-compiler
with blueprint-compiler-0.4.
* gnu/packages/text-editors.scm (textpieces): Likewise

gnu/packages/gnome.scm

@@ -3320,6 +3320,22 @@ compiles to GTKBuilder XML.")
     (home-page "https://gitlab.gnome.org/jwestman/blueprint-compiler")
     (license license:lgpl3+)))
 
+(define-public blueprint-compiler-0.4
+  (package
+    (inherit blueprint-compiler)
+    (name "blueprint-compiler")
+    (version "0.4.0")
+    (source (origin
+              (method git-fetch)
+              (uri (git-reference
+                    (url
+                     "https://gitlab.gnome.org/jwestman/blueprint-compiler")
+                    (commit (string-append "v" version))))
+              (file-name (string-append name "-" version "-checkout"))
+              (sha256
+               (base32
+                "0hj7f4xhwjc4x32r3lswwclbw37fw3spy806g4plkmym25hz4ydy"))))))
+
 (define-public cambalache
   (package
     (name "cambalache")

gnu/packages/syndication.scm

@@ -201,7 +201,7 @@ cards.")
            (list gtk "bin")
            pkg-config))
     (inputs
-     (list blueprint-compiler
+     (list blueprint-compiler-0.4
            glib
            gtk
            gtksourceview
@@ -569,7 +569,7 @@ parser.  It is \"not fit for use at this point\", but gfeeds uses it anyway.")
                 `("XDG_DATA_DIRS" ":" prefix (,(getenv "XDG_DATA_DIRS")))))))))
     (native-inputs
      (list `(,glib "bin")
-           blueprint-compiler
+           blueprint-compiler-0.4
            gobject-introspection
            gettext-minimal
            pkg-config))

gnu/packages/text-editors.scm

@@ -1065,7 +1065,7 @@ Octave.  TeXmacs is completely extensible via Guile.")
     (build-system meson-build-system)
     (native-inputs
      (list appstream-glib
-           blueprint-compiler
+           blueprint-compiler-0.4
            desktop-file-utils
            gettext-minimal
            `(,glib "bin")