use Zend/zend_smart_string.h

[remicollet]

• Zend/zend_smart_string.h exists since 7.2
• ext/standard/php_smart_string.h removed in 8.5.0alpha3

[andypost]

hit it with alpha 3

 cc -I. -I/tmp/pear/temp/yaml -I/usr/local/include/php -I/usr/local/include/php/main -I/usr/local/include/php/TSRM -I/usr/local/include/php/Zend -I/usr/local/include/php/ext -I/usr/local/include/php/ext/date/lib -DHAVE_CONFIG_H -g -O2 -D_GNU_SOURCE -DZEND_COMPILE_DL_EXT=1 -c /tmp/pear/temp/yaml/yaml.c -MMD -MF yaml.dep -MT yaml.lo  -fPIC -DPIC -o .libs/yaml.o
In file included from /tmp/pear/temp/yaml/yaml.c:35:
/tmp/pear/temp/yaml/php_yaml.h:56:10: fatal error: ext/standard/php_smart_string.h: No such file or directory
   56 | #include <ext/standard/php_smart_string.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [Makefile:209: yaml.lo] Error 1
ERROR: `make' failed