php: use TARGET_MAKE_ENV for buildconf

Otherwise we miss the PATH for hosts that lack autotools. Fixes:
http://autobuild.buildroot.net/results/368/368da962f657801817a4b962415e55606915c871/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/php/php.mk

@@ -25,7 +25,7 @@ PHP_CONF_ENV = EXTRA_LIBS="$(PHP_EXTRA_LIBS)"
 # PHP can't be AUTORECONFed the standard way unfortunately
 PHP_DEPENDENCIES += host-autoconf host-automake host-libtool
 define PHP_BUILDCONF
-	cd $(@D) ; ./buildconf --force
+	cd $(@D) ; $(TARGET_MAKE_ENV) ./buildconf --force
 endef
 PHP_PRE_CONFIGURE_HOOKS += PHP_BUILDCONF