Fix phpGH-19681 PHP_EXPAND_PATH broken with bash 5.3.0

Author: remicollet

build/php.m4

@@ -64,7 +64,11 @@ AC_DEFUN([PHP_EXPAND_PATH],[
     changequote({,})
     ep_dir=`echo $1|$SED 's%/*[^/][^/]*/*$%%'`
     changequote([,])
-    ep_realdir=`(cd "$ep_dir" && pwd)`
+    if test -z $ep_dir ; then
+      ep_realdir=`(pwd)`
+    else
+      ep_realdir=`(cd "$ep_dir" && pwd)`
+    fi
     $2="$ep_realdir"/`basename "$1"`
   fi
 ])