build: Fix GRUB i386-pc build with Ubuntu gcc

build: Fix GRUB i386-pc build with Ubuntu gcc

With recent versions of gcc on Ubuntu a very large lzma_decompress.img file is
output. (e.g. 134479600 bytes instead of 2864.) This causes grub-mkimage to
fail with: "error: Decompressor is too big."

This seems to be caused by a section .note.gnu.property that is placed at an
offset such that objcopy needs to pad the img file with zeros.

This issue is present on:
Ubuntu 19.10 with gcc (Ubuntu 8.3.0-26ubuntu1~19.10) 8.3.0
Ubuntu 19.10 with gcc (Ubuntu 9.2.1-9ubuntu2) 9.2.1 20191008

This issue is not present on:
Ubuntu 19.10 with gcc (Ubuntu 7.5.0-3ubuntu1~19.10) 7.5.0
RHEL 8.0 with gcc 8.3.1 20190507 (Red Hat 8.3.1-4)

The issue can be fixed by removing the section using objcopy as shown in
this patch.

Signed-off-by: Simon Hardy <simon.hardy@itdev.co.uk>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>