package/php: fix date.timezone

package/php: fix date.timezone

In 5f37843a (php.ini: set date.timezone), the configured timezone was
used as the default for PHP.

However, BR2_TARGET_LOCALTIME is a string, so is quoted, so it is never
empty, so the check for emptynessnever matches.

Fix that by q-stripping the value before testing it. Note however that
we do not q-strip it before storing it in the php.ini file, because it
has to be q-stripped in there.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Floris Bos <bos@je-eigen-domein.nl>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>