Revert "Reapply: [Driver] Use forward slashes in most linker arguments"

This reverts commit r345370, as it uncovered even more issues in
tests with partial/inconsistent path normalization:
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/13562
http://lab.llvm.org:8011/builders/clang-x64-windows-msvc/builds/886
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/20994

In particular, these tests seem to have failed:
    Clang :: CodeGen/thinlto-diagnostic-handler-remarks-with-hotness.ll
    Clang :: CodeGen/thinlto-multi-module.ll
    Clang :: Driver/cuda-external-tools.cu
    Clang :: Driver/cuda-options.cu
    Clang :: Driver/hip-toolchain-no-rdc.hip
    Clang :: Driver/hip-toolchain-rdc.hip
    Clang :: Driver/openmp-offload-gpu.c

At least the Driver tests could potentially be fixed by extending
the path normalization to even more places, but the issues with the
CodeGen tests are still unknown.

In addition, a number of other tests seem to have been broken in
other clang dependent tools such as clang-tidy and clangd.

llvm-svn: 345372