php: add patch to fix static library build

This commit adds a patch to PHP which fixes the build for
BR2_STATIC_LIBS=y configurations.

Fixes:

  http://autobuild.buildroot.net/results/885f418cc26c6832a8a9abf703aecbeea8fbe550/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>