[OE-core] kernel: update rpm failed for the vfat

["Xu, Yanfei" <yanfei.xu@windriver.com>]

Hi Bruce,

I encountered an issue that updating kernel rpm package will fail when 
the /boot dir was mount with vfat filesystem. The root cause is vfat 
don't support symlink.
--------cut here----------
error: unpacking of archive failed on file /boot/Image;5eda8385: cpio: 
symlink failed - Resource temporarily unavailable
error: 
kernel-image-image-5.4.43-yocto-standard-5.4.x+git0+f8c88c4331_9961cc8b79-r0.bcm_2xxx_rpi4: 
install failed
root@bcm-2xxx-rpi4:/boot#

Currently I have two ideas to fix it:
1. we use 'install' cmd instead of 'ln -sf' in kernel_do_install to 
avoid generating symlink in kernel-image-image*.rpm. And then add an 
postinstall to this rpm. It will check if the /boot dir is vfat, if not, 
we remove the copy image* and make a softlink for the image.
2. we specially add an package type which doesn't contain symlink for 
the vfat filesystem.

For the first idea, I met an problem when I try to add 
pkg_postinst_packagename function in kernel.bbclass file. Due to there 
are not package name variables defined for the kernel-image-image.gz 
kernel-image-image or other type kernel images. So I can not add 
postinst functions statically why that how many packages and packages' 
name are not certainly.

Do you have any opinions about these?


Regards,
Yanfei