Simplify python launcher, use __main__.py

Uses more python rather than C++, and skips less of Py_Main.

Test: build/soong/python/tests/runtests.sh
Change-Id: I03997d88e2e16047c96bb4e00e530229c42b3325

python/scripts/main.py

@@ -0,0 +1,12 @@
+import runpy
+import sys
+
+sys.argv[0] = __loader__.archive
+
+# Set sys.executable to None. The real executable is available as
+# sys.argv[0], and too many things assume sys.executable is a regular Python
+# binary, which isn't available. By setting it to None we get clear errors
+# when people try to use it.
+sys.executable = None
+
+runpy._run_module_as_main("ENTRY_POINT", alter_argv=False)