libpcre2: Don't use -Werror=array-bounds

pcre2test uses negative array indices which seem to confuse the array bounds
checker. The warnings look harmless.

Disable -Werror=array-bounds for libpcre2 to allow building with a global
-Werror=array-bounds.

Signed-off-by: Bernhard Rosenkränzer <bernhard.rosenkraenzer.ext@huawei.com>