Add CI test to ensure standalone composefs-boot works

[alexlarsson]

The configuration with no default options needs to keep building, and should not pick up dependencies on any other composefs crate.

[alexlarsson]

What the heck is this:

  cargo:warning=/builddir/build/BUILD/composefs-202610050730.g5764d4317a-build/composefs-rs-202610050730.g5764d4317a/vendor/aws-lc-sys/aws-lc/third_party/jitterentropy/jitterentropy-library/src/jitterentropy-base.c:47:3: error: #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
  cargo:warning=   47 |  #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
  cargo:warning=      |   ^~~~~
  exit status: 1

Is this something new?

[Johan-Liebert1]

First time seeing this. Looks like an issue on the rpm side and not ours

[alexlarsson]

Yeah, its clearly unrelated, so I'll merge this. But we need to figure out where it comes from,

[alexlarsson]

As per aws/aws-lc-rs#1252 this is caused by cc 1.6.0 and we need to pin it at 1.5.1. However we're currently not using any lockfiles at all. I wonder if we should start doing that?

[alexlarsson]

Or we can wait for aws/aws-lc-rs#1253

[cgwalters]

The Packit jobs aren't gating right now

[jeckersb]

What the heck is this:

  cargo:warning=/builddir/build/BUILD/composefs-202610050730.g5764d4317a-build/composefs-rs-202610050730.g5764d4317a/vendor/aws-lc-sys/aws-lc/third_party/jitterentropy/jitterentropy-library/src/jitterentropy-base.c:47:3: error: #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
  cargo:warning=   47 |  #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
  cargo:warning=      |   ^~~~~
  exit status: 1

Is this something new?

IIRC this happens because something earlier in the job fails to download something, so it falls back to trying to build from source and failing.

Edit: although that's the packit job so that should be in mock via known inputs, so this is something new, but related to what I said above I think.