gpg4libre: fix failing gpg test due to over-long filenames

With long workdir path, gpg sometimes fails with 'gpg: can't connect
to the agent: File name too long' error.
WK recommends to create preferred socket dir under /run/user, needs
prepping though via gpgconf.

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=84720

Change-Id: I2edb27758b2d4581d54eabf549dcdfed0106dba4
Reviewed-on: https://gerrit.libreoffice.org/50978Tested-by: Rene Engelhard <rene@debian.org>
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

xmlsecurity/CppunitTest_xmlsecurity_signing.mk

@@ -52,11 +52,21 @@ ifeq ($(ENABLE_PDFIMPORT),TRUE)
 $(eval $(call gb_CppunitTest_use_executable,xmlsecurity_signing,xpdfimport))
 endif
 
-# reset the LD_LIBRARY_PATH for spawned GPG processes
+# various hacks to make unit test work on Linux more often
 ifeq ($(OS),LINUX)
+# reset the LD_LIBRARY_PATH for spawned GPG processes
 $(call gb_CppunitTest_get_target,xmlsecurity_signing): \
     EXTRA_ENV_VARS := \
         LIBO_LD_PATH=$$LD_LIBRARY_PATH
+
+# create socket dir below /run/user/ instead of in workdir
+.PHONY : gb_CppunitTest_run_gpgconf
+gb_CppunitTest_run_gpgconf:
+	GNUPGHOME=$(WORKDIR)/CppunitTest/xmlsecurity_signing.test.user \
+	gpgconf --create-socketdir 2>/dev/null || true
+
+$(call gb_CppunitTest_get_target,xmlsecurity_signing): \
+    gb_CppunitTest_run_gpgconf
 endif
 
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