[Driver]: fix compiler-rt path when printing libgcc for baremetal

clang --target arm-none-eabi --print-libgcc-file-name --rtlib=compiler-rt
used to print `/path/to/lib/clang/version/lib/libclang_rt.builtins-arm.a`
but should print `/path/to/lib/clang/version/lib/baremetal/libclang_rt.builtins-arm.a`.
Similarly, --target armv7m-none-eabi should print libclang_rt.builtins-armv7m.a
This matches the compiler-rt file name used at link time in the
baremetal driver.

Reviewed By: manojgupta

Differential Revision: https://reviews.llvm.org/D89327