x86/boot: create *.lnk files with linker script

x86/boot: create *.lnk files with linker script

Newer GCC (e.g. gcc version 5.1.1 20150618 (Red Hat 5.1.1-4) (GCC)) does
some code optimizations by creating data sections (e.g. jump addresses
for C switch/case are calculated using data in .rodata section). This
thing is not accepted by *.lnk build recipe which requires that only .text
section lives in output. Potentially we can inhibit this GCC behavior by
using special options, e.g. -fno-tree-switch-conversion. However, this
does not guarantee that in the future new similar optimizations or anything
else which creates not accepted sections will not break our build recipes
again. I do not mention that probably this is not good idea to just disable
random optimizations. So, take over full control on *.lnk linking process
by using linker script and merge all text and data sections into one
.text section.

Additionally, remove .got.plt section which is not used in our final code.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>