Initial implementation of exec diagnostic wrapper

Demonstration:
/tmp/ene# ls -l
total 2044
-rwxr-xr-x 1 root root 1033720 Dec 17 12:37 bash_no_interp
-rw-r--r-- 1 root root 1033720 Dec 17 12:37 bash_non_executable
-rwxr-xr-x 1 root root      34 Dec 17 18:32 shebang_enoent.sh
-rwxr-xr-x 1 root root      18 Dec 17 18:31 shebang_slash_bash_no_interp.sh
-rwxr-xr-x 1 root root      21 Dec 17 18:30 shebang_recursive_slash_shebang_enoent.sh
/tmp/ene# for i in *.sh; do echo $i:; cat $i; done
shebang_enoent.sh:
shebang_slash_bash_no_interp.sh:
shebang_recursive_slash_shebang_enoent.sh:

/tmp# ./diagexec ene/ /bash_no_interp
Error: Unable to open "/lib64/ld-linux-x86-64.so.2": No such file or directory
/tmp# ./diagexec ene/ /bash_non_executable
Error: "/bash_non_executable" is not executable
/tmp# ./diagexec ene/ /shebang_enoent.sh
Error: Unable to open "/this/shebang/interp/is/missing": No such file or directory
/tmp# ./diagexec ene/ /shebang_slash_bash_no_interp.sh
Error: Unable to open "/lib64/ld-linux-x86-64.so.2": No such file or directory
/tmp# ./diagexec ene/ /shebang_recursive_slash_shebang_enoent.sh
Error: Unable to open "/this/shebang/interp/is/missing": No such file or directory
/tmp#