"cargo:rerun-if-changed" missing colon?

[barries]

Describe the bug

autocxx emits lines like:

cargo:rerun-if-changed=/usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11/bits/c++config.h
cargo:rerun-if-changed=/usr/lib/gcc/x86_64-linux-gnu/11/../../../../include/x86_64-linux-gnu/c++/11/bits/os_defines.h

when the current spec is to emit the cargo:: prefix with two colons.

To Reproduce

Cause a build.rs failure when using autocxx and examine the output.

Expected behavior

autocxx emits lines with correct prefixes.

Additional context
Add any other context about the problem here.

[tchebb]

Both forms are valid; see the note in Cargo's "Build Scripts" documentation:

MSRV: 1.77 is required for cargo::KEY=VALUE syntax. To support older versions, use the cargo:KEY=VALUE syntax.

Since autocxx has an MSRV of 1.77, they could switch to the new form, but using the old one doesn't really hurt anything.