Complete migration to Gulp 4, add linux32 support

- Remove usages of runSequence(), which doesn't work with Gulp 4,
using gulp.series() instead.
- Add support for linux32 builds
- Add new --platform argument for building only for a single platform
(e.g. --platform=osx64).

Fixes build problems introduced in #527
Fixes #531

gulpfile.js

@@ -3,6 +3,7 @@
 var child_process = require('child_process');
 var fs = require('fs');
 var path = require('path');
+var minimist = require('minimist');
 
 var archiver = require('archiver');
 var del = require('del');
@@ -10,8 +11,6 @@ var NwBuilder = require('nw-builder');
 
 var gulp = require('gulp');
 var concat = require('gulp-concat');
-var runSequence = require('run-sequence');
-
 
 // Each key in the *sources* variable must be an array of
 // the source files that will be combined into a single
@@ -159,6 +158,18 @@ function get_task_name(key) {
     return 'build-' + key.replace(/([A-Z])/g, function($1){return "-"+$1.toLowerCase();});
 }
 
+function getPlatforms() {
+    var defaultPlatforms = ['win32', 'osx64', 'linux32', 'linux64'];
+    var argv = minimist(process.argv.slice(2));
+    if (argv.platform) {
+        if (defaultPlatforms.indexOf(argv.platform) < 0) {
+            throw "Invalid platform '" + argv.platform + "'. Available ones are: " + defaultPlatforms;
+        }
+        return [argv.platform];
+    }
+    return defaultPlatforms;
+}
+
 // Define build tasks dynamically based on the sources
 // and output variables.
 var buildCssTasks = [];
@@ -192,7 +203,7 @@ gulp.task('clean', function() { return del(['./build/**', './dist/**'], {force:
 
 // Real work for dist task. Done in another task to call it via
 // run-sequence.
-gulp.task('dist-build', gulp.series('build'), function() {
+gulp.task('dist-build', gulp.series('build', function() {
     var distSources = [
         './package.json', // For NW.js
         './manifest.json', // For Chrome app
@@ -211,18 +222,16 @@ gulp.task('dist-build', gulp.series('build'), function() {
     ];
     return gulp.src(distSources, { base: '.' })
         .pipe(gulp.dest(distDir));
-});
+}));
 
-gulp.task('dist', function(done) {
-    return runSequence('clean', 'dist-build', done);
-});
+gulp.task('dist',  gulp.series('clean', 'dist-build'));
 
 // Create app directories in ./apps
-gulp.task('apps', gulp.series('dist'), function(done) {
+gulp.task('apps', gulp.series('dist', function(done) {
     var builder = new NwBuilder({
         files: './dist/**/*',
         buildDir: appsDir,
-        platforms: ['win32', 'osx64', 'linux64'],
+        platforms: getPlatforms(),
         flavor: 'normal',
         macIcns: './images/inav.icns',
         winIco: './images/inav.ico',
@@ -237,14 +246,14 @@ gulp.task('apps', gulp.series('dist'), function(done) {
         // Package apps as .zip files
         done();
     });
-});
+}));
 
 function get_release_filename(platform, ext) {
     var pkg = require('./package.json');
     return 'INAV-Configurator_' + platform + '_' + pkg.version + '.' + ext;
 }
 
-gulp.task('release-windows', function() {
+gulp.task('release-win32', function() {
     var pkg = require('./package.json');
     var src = path.join(appsDir, pkg.name, 'win32');
     var output = fs.createWriteStream(path.join(appsDir, get_release_filename('win32', 'zip')));
@@ -258,7 +267,7 @@ gulp.task('release-windows', function() {
     return archive.finalize();
 });
 
-gulp.task('release-macos', function() {
+gulp.task('release-osx64', function() {
     var pkg = require('./package.json');
     var src = path.join(appsDir, pkg.name, 'osx64', pkg.name + '.app');
     // Check if we want to sign the .app bundle
@@ -277,49 +286,28 @@ gulp.task('release-macos', function() {
     return archive.finalize();
 });
 
-gulp.task('release-linux64', function() {
-    var pkg = require('./package.json');
-    var src = path.join(appsDir, pkg.name, 'linux64');
-    var output = fs.createWriteStream(path.join(appsDir, get_release_filename('linux64', 'zip')));
-    var archive = archiver('zip', {
-        zlib: { level: 9 }
-    });
-    archive.on('warning', function(err) { throw err; });
-    archive.on('error', function(err) { throw err; });
-    archive.pipe(output);
-    archive.directory(src, 'INAV Configurator');
-    return archive.finalize();
-});
+function releaseLinux(bits) {
+    return function() {
+        var dirname = 'linux' + bits;
+        var pkg = require('./package.json');
+        var src = path.join(appsDir, pkg.name, dirname);
+        var output = fs.createWriteStream(path.join(appsDir, get_release_filename(dirname, 'zip')));
+        var archive = archiver('zip', {
+            zlib: { level: 9 }
+        });
+        archive.on('warning', function(err) { throw err; });
+        archive.on('error', function(err) { throw err; });
+        archive.pipe(output);
+        archive.directory(src, 'INAV Configurator');
+        return archive.finalize();
+    }
+}
 
-//For build only linux, without install Wine
-//run task `apps` get error
-//Error building NW apps:Error while updating the Windows icon. Wine (winehq.org) must be installed to add custom icons from Mac and Linux.
-gulp.task('release-only-linux', gulp.series('dist'), function (done) {
-    var builder = new NwBuilder({
-        files: './dist/**/*',
-        buildDir: appsDir,
-        platforms: ['linux64'],
-        flavor: 'normal',
-    });
-    builder.on('log', console.log);
-    builder.build().then(function(){
-        //Start zip app after complete
-        runSequence('release-linux64');
-    }).catch(function(err){
-        if (err) {
-            console.log("Error building NW apps:" + err);
-            done();
-            return;
-        }
-        // Package apps as .zip files
-        done();
-    });
-});
+gulp.task('release-linux32', releaseLinux(32));
+gulp.task('release-linux64', releaseLinux(64));
 
 // Create distributable .zip files in ./apps
-gulp.task('release', function() {
-    return runSequence('apps', 'release-macos', 'release-windows', 'release-linux64');
-});
+gulp.task('release', gulp.series('apps',  getPlatforms().map(function(v) { return 'release-' + v; })));
 
 gulp.task('watch', function () {
     for(var k in output) {