tools: Correct python building host tools

tools: Correct python building host tools

When we have python building tools for the host it will not check HOSTXX
variables but only XX variables, for example LDFLAGS and not
HOSTLDFLAGS.

Cc: Simon Glass <[email protected]>
Reported-by: Heiko Schocher <[email protected]>
Fixes: 1905c8fc711a ("build: Always build the libfdt python module")
Signed-off-by: Tom Rini <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Tested-by: Simon Glass <[email protected]>
Tested-by: Heiko Schocher <[email protected]>