The autoPatchelf main function which is run against all of the outputs
was pretty much tailored towards this specific setup-hook and was
relying on $prefix to be set globally.

So if you wanted to run autoPatchelf manually - let's say during
buildPhase - you would have needed to run it like this:

  prefix=/some/directory autoPatchelf

This is now more intuitive and all you need to do is run the following:

  autoPatchelf /some/directory

Signed-off-by: aszlig <aszlig@nix.build>

If you want to only run autoPatchelf on a specific path and leave
everything else alone, we now have a $dontAutoPatchelf environment
variable, which causes the postFixup hook to not run at all.

The name "dontAutoPatchelf" probably is a bit weird in conjunction with
putting "autoPatchelfHook" in nativeBuildInputs, but unless someone
comes up with a better name I keep it that way because it's consistent
with all the other dontStrip, dontPatchShebangs, dontPatchELF and
whatnot.

A specific example where this is needed is when building the Android SDK
emulator, which contains a few ARM binaries in subdirectories that
should not be patched. If we were to run autoPatchelf on all outputs
unconditionally we'd run into errors because some ARM libraries couldn't
be found.

Signed-off-by: aszlig <aszlig@nix.build>

This is to be used with the autoPatchelf command and allows to only
patch a specific file or directory without recursing into
subdirectories.

Apart from being able to run the command in a standalone way, as
detailled in the previous commit this is also needed for the Android SDK
emulator, because according to @svanderburg there are subdirectories we
don't want to patch.

The reason why I didn't use GNU getopt is that it might not be available
on all operating systems and the getopts bash builtin doesn't support
long arguments. Apart from that, the implementation for recognizing the
flag is pretty trivial and it's also using bash builtins only, so if we
want to do something really fancy someday, we can still change it.

Signed-off-by: aszlig <aszlig@nix.build>

First of all, this makes the existing documentation a bit more clear on
what autoPatchelfHook is all about, because after discussing with
@svanderburg - who wrote a similar implementation - the rationale about
autoPatchelfHook wasn't very clear in the documentation.

I also added the recent changes around being able to use autoPatchelf
manually and the new --no-recurse flag.

Signed-off-by: aszlig <aszlig@nix.build>

This function is useful if autoPatchelf is invoked during some of the
phases of a build and allows to add arbitrary shared objects to the
search path.

So far the same functionality was in autoPatchelf itself, but not
available as a separate function, so when adding shared objects to the
dependency cache one would have to do so manually.

The function also has the --no-recurse flag, which prevents recursing
into subdirectories.

Signed-off-by: aszlig <aszlig@nix.build>

While declaring it as an array doesn't do any harm in our usage, it
might be a bit confusing when reading the code.

Signed-off-by: aszlig <aszlig@nix.build>

If the file in question is not a shared object file but an ELF, we
really want to skip the file, because we won't have anything to patch
there.

For example if the file is created via "gcc -c -o foo.o foo.c", we don't
get a segment header and so far autoPatchelf was trying to patch such a
file.

By checking for missing segment headers, we're now no longer going to
attempt patching such a file.

Signed-off-by: aszlig <aszlig@nix.build>
Reported-by: Sander van der Burg <svanderburg@gmail.com>

autoPatchelfHook: Fixes/improvements for Android SDK emulator