Allow pecl like usage in ext/pdo, refs php#2955

Author: tianon

ext/pdo/Makefile.frag

@@ -7,7 +7,7 @@ PDO_HEADER_FILES= \
 
 
 $(srcdir)/pdo_sql_parser.c: $(srcdir)/pdo_sql_parser.re
-	(cd $(top_srcdir); $(RE2C) --no-generation-date -o ext/pdo/pdo_sql_parser.c ext/pdo/pdo_sql_parser.re)
+	cd $(srcdir) && $(RE2C) --no-generation-date -o pdo_sql_parser.c pdo_sql_parser.re
 
 install-pdo-headers:
 	@echo "Installing PDO headers:          $(INSTALL_ROOT)$(phpincludedir)/ext/pdo/"