freedreno: android: fix build failure on android due to python version

The freedreno gen_header.py script now only works under python3.
It contains a "print()" call which prints a blank line under python3
but prints "()" under python2.7.

However the Android build currently uses python2.

This leads to incorrect code generation and a later build error.

.../STATIC_LIBRARIES/libfreedreno_registers_intermediates/registers/adreno_common.xml.h:163:2: error: expected identifier or '('
()

Fix this by adding MESA_PYTHON3 and using it for the freedreno scripts.

Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3736>
diff --git a/Android.mk b/Android.mk
index 59d345b..c15c2b7 100644
--- a/Android.mk
+++ b/Android.mk
@@ -43,6 +43,7 @@
 
 MESA_COMMON_MK := $(MESA_TOP)/Android.common.mk
 MESA_PYTHON2 := python
+MESA_PYTHON3 := python3
 
 # Lists to convert driver names to boolean variables
 # in form of <driver name>.<boolean make variable>
diff --git a/src/freedreno/Android.registers.mk b/src/freedreno/Android.registers.mk
index 085eb5f..ffb38d0 100644
--- a/src/freedreno/Android.registers.mk
+++ b/src/freedreno/Android.registers.mk
@@ -49,37 +49,37 @@
 $(intermediates)/registers/a2xx.xml.h: $(LOCAL_PATH)/registers/a2xx.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/a3xx.xml.h: $(LOCAL_PATH)/registers/a3xx.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/a4xx.xml.h: $(LOCAL_PATH)/registers/a4xx.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/a5xx.xml.h: $(LOCAL_PATH)/registers/a5xx.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/a6xx.xml.h: $(LOCAL_PATH)/registers/a6xx.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/adreno_common.xml.h: $(LOCAL_PATH)/registers/adreno_common.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 $(intermediates)/registers/adreno_pm4.xml.h: $(LOCAL_PATH)/registers/adreno_pm4.xml $(MESA_TOP)/src/freedreno/registers/gen_header.py
 	@mkdir -p $(dir $@)
 	@echo "Gen Header: $(PRIVATE_MODULE) <= $(notdir $(@))"
-	$(hide) $(MESA_PYTHON2) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
+	$(hide) $(MESA_PYTHON3) $(MESA_TOP)/src/freedreno/registers/gen_header.py $< > $@
 
 
 LOCAL_EXPORT_C_INCLUDE_DIRS := \