Use upstream utf8proc package, as suggested in
http://source.netsurf-browser.org/libutf8proc.git/commit/?id=770e329cceaf0620c7b482589a9b17ed1d19c16d

Work around upstream's lack of a pkg-config file and update API.

--- netsurf-3.6/Makefile
+++ netsurf-3.6/Makefile
@@ -527,10 +527,9 @@
 $(eval $(call pkg_config_find_and_add,libcss,CSS))
 $(eval $(call pkg_config_find_and_add,libdom,DOM))
 $(eval $(call pkg_config_find_and_add,libnsutils,nsutils))
-$(eval $(call pkg_config_find_and_add,libutf8proc,utf8proc))
 
 # Common libraries without pkg-config support
-LDFLAGS += -lz
+LDFLAGS += -lz -lutf8proc
 
 # Optional libraries with pkgconfig
 
--- netsurf-3.6/utils/idna.c
+++ netsurf-3.6/utils/idna.c
@@ -26,7 +26,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <libutf8proc/utf8proc.h>
+#include <utf8proc.h>
 
 #include "utils/errors.h"
 #include "utils/idna.h"
--- netsurf-3.7/test/Makefile	2017-10-15 08:39:24.000000000 -0500
+++ netsurf-3.7/test/Makefile	2017-11-05 11:14:46.219013218 -0600
@@ -139,14 +139,14 @@
 	-D_XOPEN_SOURCE=600 \
 	-Itest -Iinclude -Icontent/handlers -Ifrontends -I. -I.. \
 	-Dnsgtk \
-	$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc) \
+	$(shell pkg-config --cflags libcurl libparserutils libwapcaplet libdom libnsutils) \
 	$(LIB_CFLAGS)
 TESTCFLAGS := $(BASE_TESTCFLAGS) \
 	$(COV_CFLAGS) \
 	$(COV_CPPFLAGS)
 
 TESTLDFLAGS := -L$(TESTROOT) \
-	$(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils libutf8proc) -lz \
+	$(shell pkg-config --libs libcurl libparserutils libwapcaplet libdom libnsutils) -lz -lutf8proc \
 	$(LIB_LDFLAGS)\
 	$(COV_LDFLAGS)
 
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<div class='path'>path: <a href='/guix/log/?id=95fadee0f27ea609cf19945a3a0c7c4e0fb29629'>root</a>/<a href='/guix/log/config-daemon.ac?id=95fadee0f27ea609cf19945a3a0c7c4e0fb29629'>config-daemon.ac</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/config-daemon.ac?id=95fadee0f27ea609cf19945a3a0c7c4e0fb29629&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-11-16 14:34:28 +0100'>2021-11-16</span></td><td><a href='/guix/commit/config-daemon.ac?id=472a0e82a52a3d5d841e1dfad6b13e26082a5750'>daemon: Do not deduplicate files smaller than 8 KiB.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-18 11:25:41 +0100'>2021-06-18</span></td><td><a href='/guix/commit/config-daemon.ac?id=4985a4272497bf9ba87a2190353d915da9b55906'>Start enabling substitutes from bordeaux.guix.gnu.org.</a><span class='msg-avail'>...</span></td><td>Christopher Baines</td></tr>
<tr><td><span title='2020-12-11 19:06:53 +0100'>2020-12-11</span></td><td><a href='/guix/commit/config-daemon.ac?id=26b1030012837ff3f91d2a39971358180324d730'>maint: Remove unused 'NIX_VERSION' macro.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-12-11 19:06:53 +0100'>2020-12-11</span></td><td><a href='/guix/commit/config-daemon.ac?id=dbdae9f96f11a006993b659e0e7fd5cbf467f844'>maint: Avoid macros obsolete in Autoconf 2.70.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>