build: run V8 tests with detected Python version

V8's test runner now requires Python 3. Use the Python binary we
detected that is used elsewhere in the Makefile.

PR-URL: nodejs#42740
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>

Makefile

@@ -679,21 +679,21 @@ ifneq ("","$(wildcard deps/v8/tools/run-tests.py)")
 # Related CI job: node-test-commit-v8-linux
 test-v8: v8  ## Runs the V8 test suite on deps/v8.
 	export PATH="$(NO_BIN_OVERRIDE_PATH)" && \
-		deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) $(V8_TEST_OPTIONS) \
+		$(PYTHON) deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) $(V8_TEST_OPTIONS) \
 				mjsunit cctest debugger inspector message preparser \
 				$(TAP_V8)
 	$(info Testing hash seed)
 	$(MAKE) test-hash-seed
 
 test-v8-intl: v8
 	export PATH="$(NO_BIN_OVERRIDE_PATH)" && \
-		deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) \
+		$(PYTHON) deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) \
 				intl \
 				$(TAP_V8_INTL)
 
 test-v8-benchmarks: v8
 	export PATH="$(NO_BIN_OVERRIDE_PATH)" && \
-		deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) \
+		$(PYTHON) deps/v8/tools/run-tests.py --gn --arch=$(V8_ARCH) \
 				benchmarks \
 				$(TAP_V8_BENCHMARKS)