php: intl support needs dynamic library

getArgTypeList is defined both in ext/intl/msgformat/msgformat_helpers.cpp
and icu library so add a !BR2_STATIC_LIBS dependency to
BR2_PACKAGE_PHP_EXT_INTL

Fixes:
 - http://autobuild.buildroot.org/results/628b677d1ceb8b404265d89357225e0a1dce1407



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