add #line directive to source files

[slady]

When copying sketch source files into the build directory for building, arduino-builder should add #line directives, so the compiler knows the original filename (which can help with error and warning messages and debugging symbols).
Only .ino files are pre-processed in this way now, but the other source files for building (.c, .cpp, .h) should be handled in the same way.

[per1234]

Closing as fixed by arduino/arduino-cli#1224. Thanks @slady!