patchelf: backport fix for rpath endianness

patchelf: backport fix for rpath endianness

This is backport of upstream fix introduced in commit e88d83c8b4e4
("patchelf: Check ELF endianness before writing new runpath") which
fixes broken rpath handling on big endian systems:

 $ patchelf --set-rpath '/opt/foo/bar' lxc4-start
 $ readelf -d lxc4-start
 ...
  0x1d000000 (<unknown>: 1d000000)        0x72f
 ...

Expected output, having following patch applied is:

 $ readelf -d lxc4-start
 ...
  0x0000001d (RUNPATH)                    Library runpath: [/opt/foo/bar]
 ...

Build and runtime tested on mvebu/turris-omnia, ipq40xx/glinet-b1300
and external target xrx500/nec-wx3000hp (MIPS BE).

Signed-off-by: Matthias Van Gestel <matthias.vangestel_ext@softathome.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>