package/php: opcache needs dynamic library

package/php: opcache needs dynamic library

opcache needs dynamic library since version 8.0.0 and
https://github.com/php/php-src/commit/9a06876072b9ccb023d4a14426ccb587f10882f3
otherwise the build will fail on:

/tmp/instance-4/output-1/host/opt/ext-toolchain/bin/../lib/gcc/arm-buildroot-linux-uclibcgnueabi/9.3.0/../../../../arm-buildroot-linux-uclibcgnueabi/bin/ld: /tmp/instance-4/output-1/host/bin/../arm-buildroot-linux-uclibcgnueabi/sysroot/usr/lib/libc.a(__uClibc_main.os): in function `__uClibc_fini':
__uClibc_main.c:(.text+0x15c): undefined reference to `__fini_array_start'
/tmp/instance-4/output-1/host/opt/ext-toolchain/bin/../lib/gcc/arm-buildroot-linux-uclibcgnueabi/9.3.0/../../../../arm-buildroot-linux-uclibcgnueabi/bin/ld: __uClibc_main.c:(.text+0x160): undefined reference to `__fini_array_end'

Fixes:
 - http://autobuild.buildroot.org/results/526d2e3108ff2506482d1665bcc3ed083961430f

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>