esp32: network devices pull in GNRC dependencies statically

[miri64]

Description

While compile testing #12931 we noticed that the ESP32 won't build tests/lwip anymore. The reason: All the device drivers for the SoC network devices pull in GNRC as a static dependency.

Steps to reproduce the issue

Build tests/lwip for an ESP32 board, e.g.

BOARD=esp32-wroom-32 make -C tests/lwip

Expected results

tests/lwip should not pull in any GNRC dependencies.

Actual results

From the build output in current master:

"make" -C /data/riotbuild/riotbase/sys/net/gnrc
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/netapi
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/netif
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/netif/hdr
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/netreg
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/pkt
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/pktbuf
"make" -C /data/riotbuild/riotbase/sys/net/gnrc/pktbuf_static

Versions

Current master (50c2a2c)

[miri64]

Ah proposed fix from my side would be to not make the GNRC dependencies static but to put it in their own sub-module, as we did e.g. with xbee, cc110x, etc as well.

[gschorcht]

Yeah, this is already fixed with the code deduplication PR #12955. Since PR#12955 will take some time before it is merged, I will provide a fix for the current master.

[gschorcht]

These are simply left overs from the time when I started with the complex building system and wanted to have a working network interface when I compile tests/shell with any network device.