Compiler does not detect source files overwritten by --emit

[HertzDevil]

The compiler detects whether a Crystal source file will be overwritten by the executable if an output filename is not explicitly given; #13370 makes this work on Windows and extends it to the object file after cross-compilation. But it doesn't cover the extra files generated by the --emit options (which are produced even when running a file, not just building):

$ echo 1 > test.ll
$ crystal build --cross-compile --target=x86_64-linux-gnu --emit=llvm-ir test.ll

This overwrites test.ll. The compiler should be able to take care of this too.

Speaking of which, is --cross-compile --emit=obj entirely redundant?

[straight-shoota]

I guess. But this seems like a very weird and unlikely use case. It only matters if a source file has the file extension .ll which violates the convention to name Crystal source files .cr.

This is different with binary outputs because a) you can select the output path and .cr extension is not that unlikely due to many shards having that in their name and b) source files sometimes omit the file extension to make them easily callable as an ad-hoc compiled program (via she-bang).