This commit fixes build issue because of function `bootloader_common_reset_rtc_retain_mem`
getting inlined with compiler optimization level set to `PERF` (-O2).
Build failure log:
-----------------
In function 'bootloader_common_reset_rtc_retain_mem',
inlined from 'bootloader_common_update_rtc_retain_mem' at /h/esp-idf/components/bootloader_support/src/bootloader_common_loader.c:183:13:
/h/esp-idf/components/bootloader_support/src/bootloader_common_loader.c:159:5: error: 'memset' writing 16 bytes into a region of size 0 overflows the destination [-Werror=stringop-overflow=]
159 | memset(rtc_retain_mem, 0, sizeof(rtc_retain_mem_t));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.