libnoexec: disable exec(3) for dynamically linked executables
libnoexec prevents dynamically linked executables from calling exec(3).
$ LD_PRELOAD=libnoexec.so sh -c "ls"
sh: 1: ls: Permission denied
# echo is a shell builtin
$ LD_PRELOAD=libnoexec.so sh -c "echo test"
test
None.