Revert "setup.sh introduce isELFExec, isELFDyn"

This reverts commit e1b80a5a99.

This is broken in PIE (#68513). Best to not keep it in until something
else starts using it.

pkgs/stdenv/generic/setup.sh

@@ -212,18 +212,6 @@ isELF() {
     if [ "$magic" = $'\177ELF' ]; then return 0; else return 1; fi
 }
 
-# Return success if the specified file is an ELF object
-# and its e_type is ET_EXEC (executable file)
-isELFExec() {
-    grep -ao -P '^\177ELF.{11}\x00\x02' "$1" >/dev/null
-}
-
-# Return success if the specified file is an ELF object
-# and its e_type is ET_DYN (shared object file)
-isELFDyn() {
-    grep -ao -P '^\177ELF.{11}\x00\x03' "$1" >/dev/null
-}
-
 # Return success if the specified file is a script (i.e. starts with
 # "#!").
 isScript() {