The CPU might prefetch instructions, which means it in some cases
will try to fetch instruction located after the last instruction in
flash.text.
Add dummy bytes to ensure fetching these wont result in an error,
e.g. MMU exceptions
Removes the need to know/guess the paths to these libraries. Once we are gcc 8 only, we
can remove -nostdlib and no additional arguments are needed for system libraries.
The catch is: any time IDF overrides a symbol in the toolchain sysroot, we need
an undefined linker marker to make sure this symbol is seen by linker.
Linker script generator produces build/esp32/esp32.common.ld from
components/esp32/ld/esp32.common.ld.in
This works fine until IDF is downgraded to V3.1 which uses components/esp32/ld/esp32.common.ld and
doesn't track build/esp32/esp32.common.ld at all.
At this point, the linker runs in the build/esp32 directory and "-T esp32.common.ld" picks up the
linker script generated .ld file, which causes mis-builds.
As reported on forums: https://esp32.com/viewtopic.php?f=13&t=9684&p=40105