Always compile debuginfo-tests for the host triple

Since these tests expect a working debugger, always compile them for the
host triple, assuming a working debugger is present.

This enables us to compile and run them, even when clang is, by default,
a cross-compiler (but can still target the host).

llvm-svn: 219992
GitOrigin-RevId: 63f2c2cb6599aed7db956272a6a0f541d864e69b
11 files changed