qemu: Explicitly disable libiscsi, its not in DEPENDS

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
native/nativesdk: Clear MACHINEOVERRIDES

In cases where we override variables e.g PACKAGE_ARCH
conditionally and use a MACHINEOVERRIDE to qualify the
override like

PACKAGE_ARCH_<MACHINE> = "some target PACKAGE_ARCH"

This would also be effective if this recipe is
BBEXTENDED to native or nativesdk which is undesired
This particular issue will cause wrong sysroot to be
used for nativesdk case since PACKAGE_ARCH would have
been modified and eventually changing value of
STAGING_DIR_TARGET which we use as --sysroot option
to cross and cross-canadian built SDK gcc

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
crosssdk: Clear MACHINEOVERRIDES

Without this, things like arm* can make it into OVERRIDES when we're
building a compiler to build binaries for another architecture like
x86. This can can lead to build failures dependning on the
exact configuration and overrides.

For example:

MACHINE=imx53qsb bitbake gcc-crosssdk-initial-x86_64 -e | grep EXTRA_OECONF

was showing an armv7 configuration option to gcc.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>