RIOT-OS uses part of Espressif ESP8266 RTOS SDK to build support for
this CPU. The SDK includes some vendor-provided closed source
pre-compiled libraries that we need to modify to adapt to RIOT-OS
usage. This library modifications was done once and uploaded to a fork
of the vendor repository and was provided as an environment variable.
This patch changes two things:
1. It installs the SDK as a RIOT PKG from the new pkg/esp8266_sdk
directory instead of requiring the user to download it separately.
2. It performs the library modifications (symbol renames) on the pkg
Makefile removing the need to use a fork with the modifications applied
and simplifying the SDK update and future modifications.
This change sets the SDK package version (git SHA) to the same one that
our fork was using as a parent in the vendor repository, meaning that
the output libraries are exactly the same as before.
Tested with
```
ESP8266_RTOS_SDK_DIR=/dev/null USEMODULE=esp_log_startup make -C tests/shell BOARD=esp8266-esp-12x flash
```
and verified that the program works. The boot message now includes:
```
ESP8266-RTOS-SDK Version v3.1-51-g913a06a9
```
confirming the SDK version used.
`/dev/null` in the test is just to make sure that no evaluation of
`ESP8266_RTOS_SDK_DIR` in make is affected by the environment variable
value which would be set to the SDK for people who followed the set up
instructions before this change.
Tested the checkout size:
```bash
$ du -hs build/pkg/esp8266_sdk/
124M build/pkg/esp8266_sdk/
```
Checksumming flash is not supported on xtensa platform:
Warn : not implemented yet
make: *** [.../RIOT/examples/saul/../../Makefile.include:796: flash] Error 1
Forward data soly based on the real source IPv6 address, not the virtual
MAC address.
ACK frames don't have a MAC address and should still be forwarded to all
nodes in range.
While this could theoretically be desired, it's usually just a mishap.
It is unlikely that legitimate cases will be needed in the build system;
if so, they can exclude themselves.
See-Also: https://github.com/RIOT-OS/RIOT/pull/16775
This is purely to finally unblock RIOT-OS/riotdocker#104, but may also
be useful to add future exclude patterns.
Exclude file was generated using
```sh
make doc 2> dist/tools/doccheck/exclude_patterns_base
grep "^${PWD}" dist/tools/doccheck/exclude_patterns_base | \
sed -E -e "s#^${PWD}/(.*:)([0-9]+): #\1DIGITS_MAGIC: #" \
-e 's/[]\\.$*{}|+?()[^-]/\\&/g' \
-e 's/:DIGITS_MAGIC:/:[0-9]+:/' \
> dist/tools/doccheck/exclude_patterns
rm dist/tools/doccheck/exclude_patterns_base
```
