selftest: Add helper function to create exports file for a testenv

This writes out the environment variables that are normally setup in the
testenv xterm to a file. This allows them to be sourced later.

This function is currently unused. However, it provides an alternative
replacement for the selftest-vars.sh script (which is really out of
date). I do plan to make use of this function in a subsequent patch-set.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

selftest/target/Samba.pm

@@ -639,4 +639,14 @@ sub export_envvars
 	}
 }
 
+sub export_envvars_to_file
+{
+	my ($filepath, $testenv_vars) = @_;
+	my $env_str = exported_envvars_str($testenv_vars);
+
+	open(FILE, "> $filepath");
+	print FILE "$env_str";
+	close(FILE);
+}
+
 1;