selftests/exec: use an explicit file for install

This test fails when installed, because it attempts to execute
'Makefile' (and expects that to fail).  However, the Makefile does
not get copied to the install directory.

So explicitly create a plain text file 'justafile' and use
that instead.

Signed-off-by: David Drysdale <drysdale@google.com>

tools/testing/selftests/exec/.gitignore

@@ -1,5 +1,6 @@
 subdir*
 script*
+justafile
 execveat
 execveat.symlink
 execveat.moved

tools/testing/selftests/exec/Makefile

@@ -1,6 +1,6 @@
 CFLAGS = -Wall
 BINARIES = execveat
-DEPS = execveat.symlink execveat.denatured script subdir
+DEPS = execveat.symlink execveat.denatured script justafile subdir
 all: $(BINARIES) $(DEPS)
 
 subdir:
@@ -9,6 +9,8 @@ script:
 	echo '#!/bin/sh' > $@
 	echo 'exit $$*' >> $@
 	chmod +x $@
+justafile:
+	echo 'abc' > $@
 execveat.symlink: execveat
 	ln -s -f $< $@
 execveat.denatured: execveat

tools/testing/selftests/exec/execveat.c

@@ -343,7 +343,7 @@ static int run_tests(void)
 	/* Attempt to execute directory => EACCES */
 	fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);
 	/* Attempt to execute non-executable => EACCES */
-	fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
+	fail += check_execveat_fail(dot_dfd, "justafile", 0, EACCES);
 	fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
 	fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
 				    EACCES);