runqemu fixes for toolchain and sdk uses

Another round of fixes for runqemu to support common usage models such as being called via the Eclipse plugin.

* don't immediately bail out if QB_SYSTEM_NAME isn't set (this variable is only set in a qemuboot.conf file), instead attempt to infer the correct qemu-system binary based on the machine name, rootfs name or kernel name
* always attempt to infer paths which aren't explicitly set, rather than only trying to infer them when the values in a qemuboot.conf aren't validate
* don't try and determine whether a MACHINE setting is correct when called From an sdk environment, bitbake isn't available in this context

[YOCTO #10309]

The following changes since commit b2771e17a5f301423f65be9f93c9c1b1e7f8ab93:

oeqa/selftest/lic-checksum: don't report the expected failure to errors.yp (2016-09-20 15:10:37 +0100)

are available in the git repository at:

git://git.openembedded.org/openembedded-core-contrib joshuagl/runqemu
http://cgit.openembedded.org/cgit.cgi/openembedded-core-contrib/log/?h=joshuagl/runqemu

Joshua Lock (4):
runqemu: validate paths and attempt to infer unset paths
runqemu: try and guess qemu-system binary when MACHINE isn't set
runqemu: don't try and invoke bitbake when running in a toolchain env
runqemu: don't fail during check_arg_machine()

 scripts/runqemu | 50 +++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 3 deletions(-)

2.7.4