Fix: NotSameFileSystem at clonefile

[adi-g15]

Fixes #531

Before this, using 'bun install' on a directory in different filesystem
such as tmpfs (/tmp) would have caused "Error: NotSameFileSystem".

This commit fixes that by handling this error, and at end of function it
will fall back to use copyfile (same as --backend=copyfile).

The discussion is in #531 (comment).

Credit due to @Beamnawap, who suggested me about --backend=copyfile as a fix.

Note: I think this error (NotSameFileSystem) may occur in case of clonefile_each_dir too, and should be handled there similarly:

bun/src/install/install.zig

Lines 1085 to 1087 in f5d8965

	error.NotSupported => {
	supported_method = .copyfile;
	},

changed to:

-error.NotSupported => {
+error.NotSameFileSystem, error.NotSupported => {
     supported_method = .copyfile;
},

Does it seem okay, should I add that in this PR?

[Jarred-Sumner]

I don't think this actually fixes it because the error is not generated, but it would be worth making the returned error consistent here anyway

[addy]

FYI this just broke the build