bridges: add arm64 RTTI synthesis QA harnesses

Synthesise UNO exception RTTI on macOS/arm64

RTTI::getRTTI() in the arm64 C++-UNO bridge resolved exception
type_info via dlsym(RTLD_DEFAULT, "_ZTIN...E"). On arm64 Darwin this
can never succeed: cl

Synthesise UNO exception RTTI on macOS/arm64

RTTI::getRTTI() in the arm64 C++-UNO bridge resolved exception
type_info via dlsym(RTLD_DEFAULT, "_ZTIN...E"). On arm64 Darwin this
can never succeed: clang emits the typeinfo of any keyless class -
which is every UNO exception - as hidden regardless of visibility
attributes, version scripts, or export lists, whereas the same class
gets exported typeinfo on x86_64 Darwin.

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Fix regressions and gaps found reviewing the arm64 C++-UNO bridge hardening

Substantially harden the macOS Silicon bridge

Handle arm64 HFA marshalling failure in the bridge

Switch to JIT allocation

Native Apple Silicon (arm64) support and bundled Python 3.10 baseline

Squashed combination of two efforts, applied onto trunk as a single
commit. (trunk is not intended to be buildable; this lands t

Native Apple Silicon (arm64) support and bundled Python 3.10 baseline

Squashed combination of two efforts, applied onto trunk as a single
commit. (trunk is not intended to be buildable; this lands the work for
reference/integration.)

=== Apple Silicon (macOS arm64 / AAPCS64) ===
Build plumbing: set_soenv.in + source_soenv.sh arm64 Darwin branch
(CPU=R, CPUNAME=AARCH64, OUTPATH=unxmaccr); new solenv/inc/unxmaccr.mk
and unx.mk dispatch; macro.hxx AARCH64 arch string; osarch.pm +
gbuild/platform/macosx.mk arch entries; configure.ac arm64 host
detection, Big Sur+ version math, and 11.0 deployment target.

C++/UNO bridge (new s5abi_macosx_aarch64): abi.cxx/hxx AAPCS64 classifier
(HFA + <=16B/>16B size rules), uno2cpp + call.s AArch64 trampoline,
cpp2uno incoming path + privateSnippetExecutor + AArch64 codeSnippet
codegen (x8 indirect-result handled, not displacing this/x0), share.hxx
__cxa_exception reserved-member alignment fix; Library_cpp_uno.mk +
makefile.mk wiring. sal/osl/unx/interlck.c arm64 atomics (__sync_* ->
LSE).

Externals: openssl darwin64-arm64-cc; icu arm64 little-endian. (NSS 3.39
deferred -- too old for arm64.)

Packaging/JVM: Info.plist LSMinimumSystemVersion 11.0; installer
download.pm/worker.pm/update_module_ignore_lists.pl recognize unxmaccr;
jvmfwk modern macOS JDK discovery (/Library/Java/JavaVirtualMachines +
Contents/Home probe).

The ABI/atomics/trampoline/JDK-discovery code was unit-tested natively
on an arm64 macOS host; a full AOO build (and bridgetest) was not run.
Code-signing infra (mandatory for arm64 distribution) is NOT included.

=== Bundled Python 2.7.18 -> 3.10 baseline (Unix/macOS first) ===
pyversion.mk/_dmake.mk -> 3.10.18 (single version knob). Shipped .py
fixes: imp -> types.ModuleType (pythonscript.py, pythonloader.py) and
file() -> open(); mailmerge.py Py3 email module imports + encoders.
Windows Python 3 build and the makefile.mk/d.lst/configure.ac Py3 work
are NOT included (separate, larger effort).

NOTE: macOS 11 becomes the minimum supported version. Python 3.10 is
EOL 2026-10; the version knob allows a later bump.

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