sanity.bbclass: Add ability to verify toolchain flags

sanity.bbclass: Add ability to verify toolchain flags

When attempting to use a binary toolchain, such as meta-mentor,
we want the ability to verify that the CCARGS, ASARGS and LDARGS
contain the necessary and appropriate flags.

This change specifically verifies, if set:
   TUNEABI_REQUIRED_CCARGS_tune-<tune>
   TUNEABI_REQUIRED_ASARGS_tune-<tune>
   TUNEABI_REQUIRED_LDARGS_tune-<tune>

Each of these, will be processed by the class and verified that the
selected tune's CCARGS, ASARGS, and LDARGS contains the listed item.  This
can be used to validate that the user has not accidently or otherwise
missed an argument.  Note, conflicting arguments are not verified.

Without verification it's possible for a misconfiguration to go
undetected, presenting runtime and debugging errors.

(From OE-Core rev: 226f17bfd2ceea7dc5784fbfaa8608f26b90d7f3)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>