[VarDumper] Fix failures on appveyor

Author: nicolas-grekas

Tests/Dumper/functions/dd_with_multiple_args.phpt

@@ -2,6 +2,7 @@
 Test dd() with multiple args shows line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {

Tests/Dumper/functions/dd_with_null.phpt

@@ -2,6 +2,7 @@
 Test dd() with null doesn't show line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {

Tests/Dumper/functions/dd_with_single_arg.phpt

@@ -2,6 +2,7 @@
 Test dd() with one arg doesn't show line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {

Tests/Dumper/functions/dump_with_multiple_args.phpt

@@ -2,6 +2,7 @@
 Test dump() with multiple args shows line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {

Tests/Dumper/functions/dump_with_null.phpt

@@ -2,6 +2,7 @@
 Test dump() with null doesn't show line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {

Tests/Dumper/functions/dump_with_single_arg.phpt

@@ -2,6 +2,7 @@
 Test dump() with one arg doesn't show line number
 --FILE--
 <?php
+putenv('NO_COLOR=1');
 
 $vendor = __DIR__;
 while (!file_exists($vendor.'/vendor')) {