gnu: fontconfig: Build fix for the Hurd.

* gnu/packages/patches/fontconfig-hurd-path-max.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/fontutils.scm (fontconfig): Use it.

gnu/local.mk

@@ -886,6 +886,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/foobillard++-pkg-config.patch		\
   %D%/packages/patches/foomatic-filters-CVE-2015-8327.patch	\
   %D%/packages/patches/foomatic-filters-CVE-2015-8560.patch	\
+  %D%/packages/patches/fontconfig-hurd-path-max.patch		\
   %D%/packages/patches/freeimage-unbundle.patch		\
   %D%/packages/patches/fuse-overlapping-headers.patch				\
   %D%/packages/patches/gawk-shell.patch				\

gnu/packages/fontutils.scm

@@ -296,6 +296,7 @@ (define-public fontconfig
             (uri (string-append
                    "https://www.freedesktop.org/software/fontconfig/release/fontconfig-"
                    version ".tar.bz2"))
+            (patches (search-patches "fontconfig-hurd-path-max.patch"))
             (sha256 (base32
                      "0hb700a68kk0ip51wdlnjjc682kvlrmb6q920mzajykdk0mdsmgn"))))
    (build-system gnu-build-system)

gnu/packages/patches/fontconfig-hurd-path-max.patch

@@ -0,0 +1,17 @@
+Avoid usage of PATH_MAX.
+
+Taken from https://salsa.debian.org/freedesktop-team/fontconfig/-/blob/master/debian/patches/path_max.patch
+
+Index: fontconfig-2.13.1/src/fccfg.c
+===================================================================
+--- fontconfig-2.13.1.orig/src/fccfg.c
++++ fontconfig-2.13.1/src/fccfg.c
+@@ -2231,7 +2231,7 @@ FcConfigRealFilename (FcConfig		*config,
+ 
+     if (n)
+     {
+-	FcChar8 buf[PATH_MAX];
++	FcChar8 buf[FC_PATH_MAX];
+ 	ssize_t len;
+ 
+ 	if (sysroot)