Heredocs (<<EOF) syntax in samples doesn't work on Windows when using default Git line ending settings

[lbussell]

dotnet-docker/samples/releasesapi/Dockerfile.debian-cross-arm64-x64

Lines 6 to 10 in 3e8c396

	RUN <<EOF
	dpkg --add-architecture amd64
	apt-get update
	apt-get install -y clang zlib1g-dev zlib1g-dev:amd64 gcc-x86-64-linux-gnu llvm
	EOF

1. This syntax is only used in the releasesapi samples and isn't consistent with our other samples.
2. This syntax does not work on Windows when using Git's default "checkout with CRLF, commit LF" setting.

Proposal: Remove heredocs in samples or provide a note about this in the samples README.

Workaround: Switch the file to LF line endings using your editor before building the sample.

[richlander]

I'm happy with any option. I noticed that this worked poorly on Windows when I made it was too stubborn to relent. Such surprising behavior for me.

[lbussell]

Here's the issue for that - moby/buildkit#4282

[lbussell]

[Triage] Another option is to specify the line ending for these files specifically with the .gitattributes file - e.g. https://stackoverflow.com/a/40821931

However, this could blow up if a user copies this to their repo and doesn't include the gitattributes. Since this doesn't provide a ton of value, we should just remove the Heredocs.