http/tests/xmlhttprequest/gzip-content-type.html gives a different ou…

…tput depending on Apache version

https://bugs.webkit.org/show_bug.cgi?id=276406
rdar://131423730

Reviewed by Brady Eidson and Aakash Jain.

Some of out bots recently got an updated Apache version. When this happened, 2 XHR tests dealing with
gzip-compressed responses have had a different output. In particular, the `Content-Length` HTTP header
is no longer present on the response.

Set the `ap_trust_cgilike_cl` Apache environment variable to allow CGI scripts to set the
`Content-Length` HTTP header again, for backward compatibility:
- https://httpd.apache.org/docs/current/env.html

* LayoutTests/http/conf/apache2.4-darwin-httpd.conf:

Canonical link: https://commits.webkit.org/280834@main

LayoutTests/http/conf/apache2.4-darwin-httpd.conf

@@ -33,13 +33,17 @@ LoadModule negotiation_module libexec/apache2/mod_negotiation.so
 LoadModule actions_module libexec/apache2/mod_actions.so
 LoadModule alias_module libexec/apache2/mod_alias.so
 LoadModule rewrite_module libexec/apache2/mod_rewrite.so
+LoadModule setenvif_module libexec/apache2/mod_setenvif.so
 
 <IfModule !mpm_prefork_module>
 	LoadModule mpm_prefork_module libexec/apache2/mod_mpm_prefork.so
 </IfModule>
 
 ServerName 127.0.0.1
 
+# Allow python CGI scripts to set the `Content-Length` header.
+SetEnvIf Request_URI "\.py$" ap_trust_cgilike_cl
+
 <Directory />
     Options Indexes FollowSymLinks MultiViews ExecCGI Includes
     AllowOverride All