Complete output file handling for kdesrc-build-setup

Now it supports:
* Backup existing configuration and overwrite
* Custom configuration filename.
* It even automatically falls back to a tempfile if backup fails.

kdesrc-build-setup

@@ -3,6 +3,8 @@
 use strict;
 use 5.010;
 use IO::Pipe;
+use File::Copy;
+use File::Temp qw/tempfile/;
 
 sub runDialogExecutable
 {
@@ -193,7 +195,56 @@ my @chosenModules = getListOptions(
 my $numCpus = getUserInput(
     'How many CPU cores do you wish to use for building?', '2');
 
-open my $output, '>', '/tmp/kdesrc-buildrc' or die "$!";
+my $outputFileName = "$ENV{HOME}/.kdesrc-buildrc";
+my $output; # Will be output filehandle.
+
+while (-e $outputFileName) {
+    (my $printableName = $outputFileName) =~ s/^$ENV{HOME}/~/;
+    my $outputChoice = getMenuOption(
+        "$printableName already exists, what do you want to do?",
+        [
+            backup => 'Make a backup, then overwrite with the new configuration',
+            custom => 'Write the new configuration to a different file',
+            cancel => 'Cancel setup',
+        ],
+    );
+
+    if ($outputChoice eq 'cancel') {
+        showInfo('Setup canceled');
+        exit 0;
+    }
+
+    if ($outputChoice eq 'custom') {
+        $outputFileName = getUserInput('Enter desired configuration file name.');
+        $outputFileName =~ s/^~/$ENV{HOME}/;
+    }
+
+    if ($outputChoice eq 'backup') {
+
+        copy($outputFileName, "$outputFileName~") or do {
+            my $error = "$!";
+            showInfo(<<EOF);
+Failed to make backup of $outputFileName, due to error $error.
+Configuration will be written to a temporary file instead.
+EOF
+
+            ($output, $outputFileName) = tempfile("kdesrc-buildrc-XXXX");
+        };
+
+        last;
+    }
+}
+
+# Filehandle could already be opened as a tempfile.
+if (!$output) {
+    open ($output, '>', $outputFileName) or do {
+        my $error = "$!";
+        showInfo (<<EOF);
+Unable to open output file $outputFileName for writing due to error $error.
+EOF
+        die "$!";
+    }
+}
 
 print $output <<EOF;
 # Autogenerated by kdesrc-build-setup. You may modify this file if desired.
@@ -349,3 +400,12 @@ end module-set
 
 EOF
 }
+
+close($output);
+$outputFileName =~ s/^$ENV{HOME}/~/;
+showInfo("Generated configuration has been written to $outputFileName");
+
+# Say same thing in text mode just in case.
+system('clear');
+say "Generated configuration has been written to $outputFileName";
+exit 0;