Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

externalonly.test
# RUN: llvm-nm -g %p/Inputs/hello.obj.macho-x86_64 | FileCheck %s
# RUN: llvm-nm -g -g %p/Inputs/hello.obj.macho-x86_64 | FileCheck %s

# CHECK-NOT: EH_frame0
# CHECK: _main