archivers/pecl-rar: fix build on GCC architectures

In file included from /wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/rararch.c:44:
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:15: error: redefinition of typedef 'handler_this_t'
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:15: error: previous declaration of 'handler_this_t' was here
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:19: error: redefinition of typedef 'rar_obj_ref'
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:19: error: previous declaration of 'rar_obj_ref' was here
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:46: error: redefinition of typedef 'zpp_s_size_t'
/wrkdirs/usr/ports/archivers/pecl-rar/work-php73/rar-4.2.0/php_compat.h:46: error: previous declaration of 'zpp_s_size_t' was here

MFH: 2021Q1