selftests/exec: Add non-regular to TEST_GEN_PROGS

non-regular file needs to be compiled and then copied to the output
directory. Remove it from TEST_PROGS and add it to TEST_GEN_PROGS. This
removes error thrown by rsync when non-regular object isn't found:

rsync: [sender] link_stat "/linux/tools/testing/selftests/exec/non-regular" failed: No such file or directory (2)
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1333) [sender=3.2.3]

Fixes: 0f71241a8e32 ("selftests/exec: add file type errno tests")
Reported-by: "kernelci.org bot" <[e-mail]>
Signed-off-by: Muhammad Usama Anjum <[e-mail]>
Reviewed-by: Shuah Khan <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/exec/Makefile

···
 CFLAGS += -Wno-nonnull
 CFLAGS += -D_GNU_SOURCE
 
-TEST_PROGS := binfmt_script non-regular
-TEST_GEN_PROGS := execveat load_address_4096 load_address_2097152 load_address_16777216
+TEST_PROGS := binfmt_script
+TEST_GEN_PROGS := execveat load_address_4096 load_address_2097152 load_address_16777216 non-regular
 TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir
 # Makefile is a run-time dependency, since it's accessed by the execveat test
 TEST_FILES := Makefile