[libc-commits] [libc] [libc] Allow hermetic tests to use external startup objects (PR #212557)

[Simi Pallipurath via libc-commits]

simpal01 wrote:

@kaladron @michaelrj-google 

In terms of testing this particular patch, the only practical approach we identified was the one suggested by my colleague, @smithp35 is to construct a minimal crt1.o that is just sufficient for linking. The new test  external_startup_link_test.cpp‎ s built and linked only when LLVM_LIBC_HERMETIC_TEST_USE_INTERNAL_STARTUP is disabled, using this external startup object. If LLVM libc’s internal crt1  is also linked accidentally, the duplicate _start symbol causes the link to fail. 

I’ve added the new test and the necessary changes. Could you please take a look?

https://github.com/llvm/llvm-project/pull/212557