check-blobs.sh does nothing

[jonas-schievink]

Running it modifies all the archives on my system, but doesn't fail.

Since we've started passing -g to the assembler, all files now contain system-specific paths and are not reproducible.

[adamgreig]

check-blobs.sh compares the output of arm-none-eabi-objdump -Cd, which does not contain the system-specific paths and the CI seems to be correctly checking that those outputs match, but unfortunately that's not the same as checking the actual .a files match byte-for-byte. Can we specify -g without causing specific paths to be included?