insane: Rationalise phdrs-based QA checks

insane: Rationalise phdrs-based QA checks

Various different QA checks are based on essentially the same data from
the ELF program headers.  Calling objdump to extract it repeatedly is
inefficient, particularly if the shell is involved.  Instead, let's
cache the output from objdump inside the qa.elf object and allow it to
be reused by multiple tests.

Also, using objdump instead of scanelf to check for bad RPATHs (in the
same way that the useless-rpaths check was doing already) allows the
dependency on pax-utils-native to be dropped.

(From OE-Core rev: bf19eeb9f65e91bf2b5d89e7c0b099c55d7c15ff)

Signed-off-by: Phil Blundell <philb@gnu.org>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>