GCC: Add value profile support for kernel.

GCC inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I734PM



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This feature add value profile support for kernel by changing GCOV
option "-fprofile-arcs" to "-fprofile-generate" when the new added
config "PGO_KERNEL" is set to y.

Like GCOV, the symbols required by value profile are migrated from
GCC source codes as they cannot be linked to kernel. Specifically,
from libgcc/libgcov-profiler.c to kernel/gcov/gcc_base.c.

kernel options:
CONFIG_PGO_KERNEL=y

Signed-off-by: Xiong Zhou <xiongzhou4@huawei.com>
Reviewed-by: Li Yancheng <liyancheng@huawei.com>