[flang-commits] [flang] [flang][driver] Fix Driver/isysroot.f90 test (PR #78478)

[Leandro Lupori via flang-commits]

luporl wrote:

Tested on MacOS. When DEFAULT_SYSROOT is set isysroot.f90 becomes unsupported and when not set the test passes.

https://github.com/llvm/llvm-project/pull/78478