prereq-build: add python 3.9 support

Fixes unmet dependency issue.

Signed-off-by: Rosen Penev <[email protected]>

include/prereq-build.mk

@@ -149,6 +149,7 @@ $(eval $(call SetupHostCommand,perl,Please install Perl 5.x, \
 $(eval $(call CleanupPython2))
 
 $(eval $(call SetupHostCommand,python,Please install Python >= 3.5, \
+	python3.9 -V 2>&1 | grep 'Python 3', \
 	python3.8 -V 2>&1 | grep 'Python 3', \
 	python3.7 -V 2>&1 | grep 'Python 3', \
 	python3.6 -V 2>&1 | grep 'Python 3', \
@@ -156,6 +157,7 @@ $(eval $(call SetupHostCommand,python,Please install Python >= 3.5, \
 	python3 -V 2>&1 | grep -E 'Python 3\.[5-9]\.?'))
 
 $(eval $(call SetupHostCommand,python3,Please install Python >= 3.5, \
+	python3.9 -V 2>&1 | grep 'Python 3', \
 	python3.8 -V 2>&1 | grep 'Python 3', \
 	python3.7 -V 2>&1 | grep 'Python 3', \
 	python3.6 -V 2>&1 | grep 'Python 3', \