package/pcre2: fix build on mips r6

Fix build of pcre2 10.35 on mips r6:
https://bugs.exim.org/show_bug.cgi?id=2667

Fixes:
 - http://autobuild.buildroot.org/results/eab208c050867c9bd12bd80dca33cbe0199b0a7d



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>