Of course, saw right after my last message that the dependency cycle here is
through poppler, and cairo-sans-poppler exists. So I think I've solved this
problem and will submit a patch.
I've attached the current changes I've been working on and testing for now.
diff --git a/gnu/packages/glib.scm b/gnu/packages/glib.scm
index 206222b578..fb3dbdecb5 100644
--- a/gnu/packages/glib.scm
+++ b/gnu/packages/glib.scm
@@ -496,6 +496,13 @@ dynamic loading, and an object system.")
(arguments
`(#:phases
(modify-phases %standard-phases
+ (add-after 'unpack 'patch
+ ;; Patch for cairo library location
+ (lambda* (#:key inputs #:allow-other-keys)
+ (substitute* "gir/cairo-1.0.gir.in"
+ (("shared-library=\"@CAIRO_SHARED_LIBRARY@\"")
+ (string-append "shared-library=\""
+ (assoc-ref inputs "cairo") "/lib/@CAIRO_SHARED_LIBRARY@\"")))))
(add-after 'unpack 'do-not-use-/usr/bin/env
(lambda _
(substitute* "tools/g-ir-tool-template.in"
@@ -507,6 +514,7 @@ dynamic loading, and an object system.")
("pkg-config" ,pkg-config)))
(inputs
`(("bison" ,bison)
+ ("cairo" ,cairo-sans-poppler) ; break dependency loop via poppler
("flex" ,flex)
("glib" ,glib)
("python" ,python-wrapper)
