clang-offload-bundler is not only used by clang driver
to bundle/unbundle files for offloading toolchains,
but also used by out of tree tools to unbundle
fat binaries generated by clang. It is important
to be able to list the bundle IDs in a bundled
file so that the bundles can be extracted.
This patch adds an option -list to list bundle
ID's in a bundled file. Each bundle ID is separated
by new line. If the file is not a bundled file
nothing is output and returns 0.