Fix valgrind FATE for out-of-tree builds.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

configure

@@ -3243,7 +3243,7 @@ fi
 
 enabled debug && add_cflags -g"$debuglevel" && add_asflags -g"$debuglevel"
 enabled coverage && add_cflags "-fprofile-arcs -ftest-coverage" && add_ldflags "-fprofile-arcs -ftest-coverage"
-test -n "$valgrind" && target_exec="$valgrind --error-exitcode=1 --malloc-fill=0x2a --track-origins=yes --leak-check=full --gen-suppressions=all --suppressions=tests/fate-valgrind.supp"
+test -n "$valgrind" && target_exec="$valgrind --error-exitcode=1 --malloc-fill=0x2a --track-origins=yes --leak-check=full --gen-suppressions=all --suppressions=$source_path/tests/fate-valgrind.supp"
 
 # add some useful compiler flags if supported
 check_cflags -Wdeclaration-after-statement