added clean build option using --clean flag in efr32_examples

[lpbeliveau-silabs]

Adds a new flag to do a clean build up when specifying : --clean when using the gn_efr32_example.sh script to build examples.

[CLAassistant]

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[jmartinez-silabs]

Why are we not just using scripts/build/build_examples.py. That script has standardised arguments across many platforms and in particular will support --clean.

It is difficult to maintain several different scripts with several different arguments. As a core developer, remembering each argument for scripts/examples (I see android, efr32, psoc6, k32w, imxlinx, webos, nrfconnect, boufallolab there) is tedious.

@andy31415 We do maintain build_examples.py for the Silabs platform also and yes it is standardized and for stuff like CI, it is great. However, it doesn't allow as much flexibility for us. Each combination of arguments becomes a new string in the target name and It becomes even more tedious to remember the naming. If you type a wrong target name you get an error message and it prints hundreds of target names for every platform and argument combination.

With our own script that we maintain, we can provide presets that we do want to showcase but also complete flexibility in any arguments you would want to add or remove.

[stale[bot]]

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