[dsymutil] Copy eh_frame content into the dSYM companion file.

Copy over the __eh_frame from the binary into the dSYM. This helps
kernel developers that are working with only dSYMs (i.e. no binaries)
when debugging a core file. This only kicks in when the __eh_frame
exists in the linked binary. Most of the time ld64 will remove the
section in favor of compact unwind info. When it is emitted, it's
generally small enough and should not bloat the dSYM.

rdar://69774935

Differential revision: https://reviews.llvm.org/D94460