shim: build as Position-Independent-Executable
shim: build as Position-Independent-Executable

Build the shim binary as Position-Independent-Executable (PIE) for improved
security and compliancy with distros packaging guidelines.

Fixes: #118

Signed-off-by: Marco Vedovati <7ad294ca8ed51ab6f7b6cc42294ec572c85df1f5@suse.com>

amshinde/shim,amshinde/shim