sapi/apache2handler: Add --disable-apache2-conf configure option

Add a new --disable-apache2-conf option that prevents apxs from editing
httpd.conf during installation. When SYSCONFDIR is non-empty, apxs is
invoked with -a, which requires httpd.conf to exist at the target path.
This fails when installing into a staging directory (INSTALL_ROOT) where
no `httpd.conf` exists but apxs is present and works, and is also
unwanted on distributions [like Debian][1] that manage Apache module
activation separately (e.g. via a2enmod).

[1]: https://salsa.debian.org/php-team/php/-/blob/9bd72dc78216cf136315d765ec3a602ac99e60e3/debian/patches/0030-Add-patch-to-install-php7-module-directly-to-APXS_LI.patch

Assisted-by: Claude Sonnet 4.6

Author: paulmenzel

sapi/apache2handler/config.m4

@@ -6,6 +6,15 @@ PHP_ARG_WITH([apxs2],
   [no],
   [no])
 
+PHP_ARG_ENABLE([apache2-conf],
+  [whether to activate the PHP module in Apache httpd.conf via apxs],
+  [AS_HELP_STRING([--disable-apache2-conf],
+    [Do not activate the PHP module in the Apache httpd.conf during installation
+    via apxs. Useful when installing into a staging directory or when Apache
+    configuration is managed separately (e.g., via a2enmod).])],
+  [yes],
+  [no])
+
 if test "$PHP_APXS2" != "no"; then
   AS_VAR_IF([PHP_APXS2], [yes], [
     APXS=apxs
@@ -69,7 +78,7 @@ if test "$PHP_APXS2" != "no"; then
     [AC_MSG_ERROR([Please note that Apache version >= 2.4 is required])])
 
   APXS_LIBEXECDIR='$(INSTALL_ROOT)'$($APXS -q LIBEXECDIR)
-  if test -z $($APXS -q SYSCONFDIR); then
+  if test -z $($APXS -q SYSCONFDIR) || test "$PHP_APACHE2_CONF" = "no"; then
     INSTALL_IT="\$(mkinstalldirs) '$APXS_LIBEXECDIR' && \
                  $APXS -S LIBEXECDIR='$APXS_LIBEXECDIR' \
                        -i -n php"