Fix fakeroot build by using od(1) to check 64-bit ELFs

[JohnoKing]

bin/package:

• Use od to check the ELF header if file fails with an error. This allows ksh to build and install correctly in fakeroot environments without encountering bogus seccomp restrictions.

Fixes #919

[McDutchie]

How is -A n more portable than -An? Is there a specific system on which it fails?

Option grouping is part of the POSIX Utility Syntax Guidelines (Guideline 5), which od is expected to follow, so this should work everywhere, just like -tx1 (which you didn't change to -t x1 in locale.sh).

[McDutchie]

Also, why use od instead of file --no-sandbox as the fallback? Hasn't the latter been shown to work already?

If so, the following should be enough, shouldn't it?

diff --git a/bin/package b/bin/package
index a40139161..149e31025 100755
--- a/bin/package
+++ b/bin/package
@@ -1523,7 +1523,9 @@ int b(void) { return 0; }
 					echo 'int main(void) { return 0; }' > $tmp.a.c
 					checkcc
 					$cc $CCFLAGS -o $tmp.a.exe $tmp.a.c </dev/null >/dev/null 2>&1
-					file $tmp.a.exe 2>/dev/null | sed "s/$tmp\.a\.exe//g"  )
+					{
+						file $tmp.a.exe || file --no-sandbox $tmp.a.exe
+					} 2>/dev/null | sed "s/$tmp\.a\.exe//g"  )
 				case $bits in
 				*\ 64-bit* | *\ 64\ bit* | *\ 64bit*)
 					bits=64 ;;

[JohnoKing]

Also, why use od instead of file --no-sandbox as the fallback?

od is more portable than file --no-sandbox (the latter is Linux-specific), so the od version can be used as a fallback on any ELF-using system that provides a defective file command (though I'm not aware of any other defective file implementations beside Linux's).

The use of -A n is because I was concerned about the possibility of an older/obsolete OS lacking a properly POSIX-compliant version of od -A. That probably doesn't matter though, so I'll revert that change.

[McDutchie]

od is more portable than file --no-sandbox (the latter is Linux-specific),

I'm seeing it on macOS and FreeBSD as well.

In any case, since we're trying file without options first (in the patch above), and only falling back to file --no-sandbox if that fails, I don't really see how that's relevant.

[JohnoKing]

I'm seeing it on macOS and FreeBSD as well.

You're apparently correct, the option is available (I should have checked). However, I don't think it does anything there; the --no-sandbox flag is meant to disable seccomp, which is available on neither FreeBSD nor macOS (the man page says it's a no-op if seccomp is unavailable). This makes a --no-sandbox fallback effectively Linux-only, even if it technically "works" on other operating systems lacking seccomp. The od fallback comparatively is more platform-neutral and could be worthwhile if file fails due to some reason other than seccomp (though I'll admit that's unlikely).

[McDutchie]

Alright then, in it goes, for more resilience against potential other forms of file(1) breakage.