To answer my own question above...
Just edit the install.php script and comment out lines 315-327
if(function_exists('apache_get_modules')) {
if(in_array('mod_rewrite', apache_get_modules())) $this->ok("Found Apache module: mod_rewrite");
else $this->err("Apache mod_rewrite does not appear to be installed and is required by ProcessWire.");
} else {
// apache_get_modules doesn't work on a cgi installation.
// check for environment var set in htaccess file, as submitted by jmarjie.
$mod_rewrite = getenv('HTTP_MOD_REWRITE') == 'On' || getenv('REDIRECT_HTTP_MOD_REWRITE') == 'On' ? true : false;
if($mod_rewrite) {
$this->ok("Found Apache module (cgi): mod_rewrite");
} else {
$this->err("Unable to determine if Apache mod_rewrite (required by ProcessWire) is installed. On some servers, we may not be able to detect it until your .htaccess file is place. Please click the 'check again' button at the bottom of this screen, if you haven't already.");
}
}
and lines 356-365
if(!is_file("./.htaccess") || !is_readable("./.htaccess")) {
if(@rename("./htaccess.txt", "./.htaccess")) $this->ok("Installed .htaccess");
else $this->err("/.htaccess doesn't exist. Before continuing, you should rename the included htaccess.txt file to be .htaccess (with the period in front of it, and no '.txt' at the end).");
} else if(!strpos(file_get_contents("./.htaccess"), "PROCESSWIRE")) {
$this->err("/.htaccess file exists, but is not for ProcessWire. Please overwrite or combine it with the provided /htaccess.txt file (i.e. rename /htaccess.txt to /.htaccess, with the period in front).");
} else {
$this->ok(".htaccess looks good");
}