Add prebuilts for darwin-arm64 python launchers

When enabling embedded_launcher: true by default for python binaries,
some darwin-arm64 builds fail because there's no python launcher
for darwin-arm64. However, the x86 prebuilt is actually a fat binary
with both architectures:

$ file py3-launcher-autorun64
py3-launcher-autorun64: Mach-O universal binary with 2 architectures: [x86_64:\012- Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|WEAK_DEFINES|BINDS_TO_WEAK|PIE>] [\012- arm64]

So we can use the x86 launchers on arm as well.

Bug: 331488610
Test: Will run abtd on the mac build that failed before
Change-Id: I755e4729cef563a644bc6861b906179da06b385b
1 file changed