x86, build: replace Perl script with Shell script

x86, build: replace Perl script with Shell script

Commit e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd")
added Perl to the required build environment.  This reimplements in
shell the Perl script used to find the size of the kernel with bss and
brk added.

Signed-off-by: Kees Cook <[email protected]>
Reported-by: Rob Landley <[email protected]>
Acked-by: Rob Landley <[email protected]>
Cc: Anca Emanuel <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Junjie Mao <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>