build: prereq: add support for Python 3.8

Add support for Python 3.8 which was released Oct. 14, 2019.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
[added missing commit description, simplified version check]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

include/prereq-build.mk

@@ -144,12 +144,14 @@ $(eval $(call SetupHostCommand,perl,Please install Perl 5.x, \
 $(eval $(call CleanupPython2))
 
 $(eval $(call SetupHostCommand,python,Please install Python >= 3.5, \
+	python3.8 -V 2>&1 | grep 'Python 3', \
 	python3.7 -V 2>&1 | grep 'Python 3', \
 	python3.6 -V 2>&1 | grep 'Python 3', \
 	python3.5 -V 2>&1 | grep 'Python 3', \
 	python3 -V 2>&1 | grep -E 'Python 3\.[5-9]\.?'))
 
 $(eval $(call SetupHostCommand,python3,Please install Python >= 3.5, \
+	python3.8 -V 2>&1 | grep 'Python 3', \
 	python3.7 -V 2>&1 | grep 'Python 3', \
 	python3.6 -V 2>&1 | grep 'Python 3', \
 	python3.5 -V 2>&1 | grep 'Python 3', \