gcov: Add coverage support for arc nsim platform

* add toolchain abstraction for coverage
* add select HAS_COVERAGE_SUPPORT to kconfig
* port gcov linker code to CKake for arc
* give user permission to gcov bss section
* expand the size of iccm and dccm to 1M

Signed-off-by: Jingru Wang <jingru@synopsys.com>