This commit provides an alternate platform identification mechanism so
"sys.implementation._mpy" will report the running target type in all
cases.

Before these changes the target type was inferred from which kind of
native emitter was enabled, since there can be only just one available
at all times and it has to be the correct one otherwise generated code
would crash the target.  However, with the introduction of RV64 there is
now a platform without an emitter, and thus RV64 targets would not be
able to report their platform via "sys.implementation._mpy".  The target
is reported only if the interpreter is configured to load external MPY
code.

Whilst this is probably not directly affecting user-facing code, some
infrastructure components like the testing framework and its associated
feature scripts rely on this feature to properly execute test runs.
This is also a concern for situations in which loading external binary
code is needed but all code generation functions have to be disabled.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This commit forces a data/instruction cache flush after loading native
code blocks even if there's no emitter available.

Caches flush upon native code load was still tied to the presence of a
native emitter, but this assumption is no longer valid due to previous
commits decoupling native code loading from code generation
availability.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This commit lets the Unix port use the new
MICROPY_PERSISTENT_CODE_LOAD_NATIVE configuration entry.

The Unix port needs to allocate memory with specific flags that let the
operating system run executable code from there.  This functionality was
gated behind the presence of a native emitter and thus its inclusion
condition had to be updated.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This commit modifies the QEMU port makefile to let the user provide
their own list of natmods to test as part of "test_natmod".

The makefile now will replace the list of natmods to test with the
contents of the "TEST_NATMODS" command line variable, so if there's a
specific subset of natmods causing problems test runs can be limited to
that very subset.  "TEST_NATMODS" accepts a whitespace-separated list of
natmod names for which there are available matching tests in
"tests/extmod" (eg. make test_natmod TEST_NATMODS="btree heapq").

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This commit lets the ESP8266 port use the new
MICROPY_PERSISTENT_CODE_LOAD_NATIVE configuration entry.

The ESP8266 port needs a special procedure to allocate memory used to
hold executable native code.  This functionality was gated behind the
presence of a native emitter and thus its inclusion condition had to be
updated.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This commit lets the nRF port use the new
MICROPY_PERSISTENT_CODE_LOAD_NATIVE configuration entry.

The nRF port needs a special procedure to allocate memory used to hold
executable native code.  This functionality was gated behind the
presence of a native emitter and thus its inclusion condition had to be
updated.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

This change lets the natmod test runner report status information on
session end if a prelude script file is chosen.

The script serialises its input data as part of the end of session
reporting data, but since the prelude file is not a serialisable object
serialisation would fail (it's a file handle as far as the argument
container structure is aware).

Now the file is explicitly open by the script rather than relying on
argparse's file handle argument class wrapper.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>