gnu: groff-minimal: Disable relocatability.

* gnu/packages/groff.scm (groff-minimal)[arguments]<#:phases>
[disable-relocatability]: New phase.

gnu/packages/groff.scm

@@ -96,6 +96,36 @@ is usually the formatter of \"man\" documentation pages.")
        ,@(substitute-keyword-arguments (package-arguments groff)
            ((#:phases phases)
             `(modify-phases ,phases
+               (add-after 'unpack 'disable-relocatability
+                 (lambda _
+                   ;; Groff contains a Rube Goldberg-esque relocator for the
+                   ;; file "charset.alias".
+                   ;; It tries to find the current executable using realpath,
+                   ;; a do-it-yourself search in $PATH and so on.
+                   ;; Furthermore, the routine that does the search is buggy
+                   ;; in that it doesn't handle error cases when they arise.
+                   ;; This causes preconv to segfault when trying to look up
+                   ;; the file "charset.alias" in the NULL location.
+                   ;; The "charset.alias" parser is a copy of gnulib's, and a
+                   ;; non-broken version of gnulib's "charset.alias" parser
+                   ;; is part of glibc's libcharset.
+                   ;; However, groff unconditionally uses their own
+                   ;; "charset.alias" parser, but then DOES NOT INSTALL the
+                   ;; file "charset.alias" when glibc is too new.
+                   ;; In Guix, our file "charset.alias" only contains an
+                   ;; obscure alias for ASCII and nothing else.
+                   ;; So just disable relocation and make the entire
+                   ;; "charset.alias" lookup fail.
+                   ;; See <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=30785>
+                   ;; for details.
+                   (substitute* "src/libs/libgroff/Makefile.sub"
+                    (("-DENABLE_RELOCATABLE=1") ""))
+                   ;; That file contains a crash bug--so make sure that
+                   ;; its contents are not there.
+                   (call-with-output-file "src/libs/libgroff/relocate.cpp"
+                     (lambda (port)
+                       #t))
+                   #t))
                (add-after 'install 'remove-non-essential-programs
                  (lambda* (#:key outputs #:allow-other-keys)
                    ;; Keep only the programs that man-db needs at run time,