Big update

src/basic/filesystem.h

@@ -19,15 +19,20 @@ struct FileIter {
 };
 
 String   ReadFile(Allocator arena, String path);
+bool     WriteFile(String path, String data);
 String   GetAbsolutePath(Allocator arena, String relative);
 bool     IsValid(const FileIter &it);
 void     Advance(FileIter *it);
 FileIter IterateFiles(Allocator allocator, String path);
 bool     InitOS();
 
+String GetExePath(Allocator allocator);
+String GetExeDir(Allocator allocator);
+
 struct Process {
-    bool is_valid;
-    char platform[32];
+    bool   is_valid;
+    String error_message;
+    char   platform[32];
 };
 
 Process RunEx(String cmd);