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
