[OE-core] Change to kernel.bbclass broke kernel build when gcc does not support -ffile-prefix-map

[Andrew Goodbody]

My build uses a version of gcc that does not support -ffile-prefix-map and this is now broken after I updated the tree to include the latest commit to kernel.bbclass "improve reproducibility" 012a70da7ae0617 by Juro Bystricky.

The patch introduces the line
cc_option_supported=`${KERNEL_CC} -Q --help=joined | grep ffile-prefix-map`
When gcc does not support -ffile-prefix-map, the grep will exit with a non-zero return code which is caught and causes the do_compile step to fail.

Thanks,
Andrew