insane.bbclass: fix HOST_ variable names
Commit cd25e554 ("insane: use HOST_ variables, not TARGET_ to determine the cross system") updated the variables themselves, but not their names. To prevent confusion, match the Python variable name to the BitBake variable name. Signed-off-by: Emil Kronborg <emil.kronborg@protonmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>