Building mpy-cross automatically leads to some issues with the build
process and slows it down.  Instead, require it to be built manually.

From https://github.com/ARM-software/CMSIS_5.git, tag 5.5.1

This adds support for SD cards using the ESP32's built-in hardware SD/MMC
host controller, over either the SDIO bus or SPI.  The class is available
as machine.SDCard and using it can be as simple as:

    uos.mount(machine.SDCard(), '/sd')

These are core configurations providing PYBv1.x-level features.

If the board-pin name is left empty then only the cpu-pin name is used, eg
",PA0".  If the board-pin name starts with a hyphen then it's available as
a C definition but not in the firmware, eg "-X1,PA0".

Because py/mpconfig.h has header include guards.

The patch solves the problem where multiple Timer objects (e.g. multiple
Timer(0) instances) could initialise multiple handles to the same internal
timer.  The list of timers is now maintained not for "active" timers (where
init is called), but for all timers created.  The timers are only removed
from the list of timers on soft-reset (machine_timer_deinit_all).

Fixes #4078.

To enable define MICROPY_HW_USB_CDC_NUM to 3.

The board config option MICROPY_HW_USB_ENABLE_CDC2 is now changed to
MICROPY_HW_USB_CDC_NUM, and the latter should be defined to the maximum
number of CDC interfaces to support (defaults to 1).

mpy-cross uses MICROPY_DYNAMIC_COMPILER and MICROPY_EMIT_NATIVE but does
not actually need to execute native functions, and does not need
mp_fun_table.  This commit makes it so mp_fun_table and all its entries are
not built when MICROPY_DYNAMIC_COMPILER is enabled, significantly reducing
the size of the mpy-cross executable and allowing it to be built on more
machines/OS's.

Otherwise flushing and disabling the D-cache will give a hard-fault when
SDRAM is used.

Fixes #4818.

In d5f0c87b this call to tcp_poll() was
added to put a timeout on closing TCP sockets.  But after calling
tcp_close() the PCB may be freed and therefore invalid, so tcp_poll() can
not be used at that point.  As a fix this commit calls tcp_poll() before
closing the TCP PCB.  If the PCB is subsequently closed and freed by
tcp_close() or tcp_abort() then the PCB will not be on any active list and
the callback will not be executed, which is the desired behaviour (the
_lwip_tcp_close_poll() callback only needs to be called if the PCB remains
active for longer than the timeout).

Commit 2848a613 introduced a bug where
lwip_socket_free_incoming() accessed pcb.tcp->state after the PCB was
closed.  The state may have changed due to that close call, or the PCB may
be freed and therefore invalid.  This commit fixes that by calling
lwip_socket_free_incoming() before the PCB is closed.

EAGAIN should be for pure non-blocking mode and ETIMEDOUT for when there is
a finite (but non-zero) timeout enabled.

These are incorrect since 5a2599d9

Set the active MPU region to the actual size of SDRAM configured and
invalidate the rest of the memory-mapped region, to prevent errors due to
CPU speculation.  Also update the attributes of the SDRAM region as per ST
recommendations, and change region numbers to avoid conflicts elsewhere in
the codebase (see eth usage).

Fixes issue #4795.

I2C can't be enabled in prj_base.conf because it's a board-specific
feature.  For example, if a board doesn't have I2C but CONFIG_I2C=y then
the build will fail (on Zephyr build system side).  The patch here gets the
qemu_cortex_m3 build working again.

So it fits better with existing narrative.

A global definition of MP_NOINLINE was added to py/mpconfig.h long ago in
0f5bf1aa

This enables going back to previous wrapped lines using backspace or left
arrow: instead of just sticking to the beginning of a line, the cursor will
move a line up.

This ; make Windows compilation fail with GNU makefile 4.2.1.  It was added
in 0dc85c9f as part of a shell if-
statement, but this if-statement was subsequently removed in
23a693ec so the semicolon is not needed.

The variable $(TOUCH) is initialized with the "touch" value in mkenv.mk
like for the other command line tools (rm, echo, cp, mkdir etc).  With
this, for example, Windows users can specify the path of touch.exe.

As part of this, ctrl-C is now able to interrupt a running program.

Defining NRFX_STATIC_ASSERT macro to be empty, but available
to nrfx.