[symbolizer] Check existence of input file in GNU mode

[symbolizer] Check existence of input file in GNU mode

GNU addr2line exits immediately if it cannot open the file specified as
executable/relocatable. In contrast llvm-addr2line does not exit and, if
addresses are not specified in command line, waits for input on stdin. This
causes the test compiler-rt/test/asan/TestCases/Posix/asan-symbolize-bad-path.cc to block
forever on Gentoo (see https://reviews.llvm.org/rG27c4777f41d2ab204c1cf84ff1cccd5ba41354da#1190273).
To fix this issue the behavior llvm-addr2line now exits if
executable/relocatable file cannot be found.

It fixes https://github.com/llvm/llvm-project/issues/42099 (llvm-addr2line
does not exit when passed a non-existent file).

Differential Revision: https://reviews.llvm.org/D147652