js,gg: more work on porting gg to JS backend (#12903)

vlib/os/environment.js.v

@@ -3,6 +3,7 @@ module os
 $if js_node {
 	#global.$ENV = $process.env
 } $else {
+	#const global = $global;
 	#global.$ENV = {}
 }
 

vlib/os/file.js.v

@@ -7,8 +7,9 @@ pub mut:
 	is_opened bool
 }
 
-#const $buffer = require('buffer');
-
+$if !js_browser {
+	#const $buffer = require('buffer');
+}
 // todo(playX):   __as_cast is broken here
 /*
 pub struct ErrFileNotOpened {

vlib/os/os.js.v

@@ -1,8 +1,10 @@
 module os
 
-#const $fs = require('fs');
-#const $path = require('path');
-#const tty = require('tty')
+$if js_node {
+	#const $fs = require('fs');
+	#const $path = require('path');
+	#const tty = require('tty')
+}
 
 pub const (
 	path_delimiter = '/'

vlib/os/process.js.v

@@ -1,6 +1,8 @@
 module os
 
-#const $child_process = require('child_process')
+$if js_node {
+	#const $child_process = require('child_process')
+}
 
 // new_process - create a new process descriptor
 // NB: new does NOT start the new process.