package/php-*: fix autoconf variables

package/php-*: fix autoconf variables

Build of php-* packages are broken since commit
3292f3de499717360cf18d7fecd79ac096216ca8 because
$(HOST_DIR)/bin/auto{conf,header} have been replaced by
$(HOST_DIR)/bin/auto{conf,header} -I "$(ACLOCAL_DIR)" -I "$(ACLOCAL_HOST_DIR)"

So revert this change (which should have been only refactoring) for
those packages

Fixes:
 - http://autobuild.buildroot.org/results/0d5f4a792652e302b8c00c1e0f99966cc930fbac
 - http://autobuild.buildroot.org/results/91a559183db212803a90cb399a1cb505b14818d9

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