Skip --disable-new-dtags on Windows when TBB_LIB is set

[jgabry]

Summary

Fixes #3414.

When TBB_LIB is set, make/compiler_flags adds -Wl,--disable-new-dtags
on every OS except macOS. On Windows both Rtools linkers reject it and every link
against an external TBB fails.

Noticed this when working on stan-dev/cmdstanr#1286.

Tests

There's no new test. The change is to the makefiles only, and CI doesn't
set TBB_LIB on Windows.

I had Claude check the resulting flags by including make/compiler_flags in a
small makefile and printing LDFLAGS_TBB with TBB_LIB=/x/lib:

Windows_NT: [-Wl,-L,/x/lib  ]
Linux:      [-Wl,-L,/x/lib -Wl,--disable-new-dtags -Wl,-rpath,/x/lib]
Darwin:     [-Wl,-L,/x/lib  -Wl,-rpath,/x/lib]

Side Effects

I don't think so. Linux and macOS get the same flags as before, and there's no effect for Windows
builds that don't set TBB_LIB.

Release notes

Setting TBB_LIB on Windows no longer adds --disable-new-dtags, which
the MinGW linkers reject.

Checklist

(I left some of the boxes unchecked since this is just a makefile change)

• Copyright holder: Jonah Gabry

  The copyright holder is typically you or your assignee, such as a university or company. By submitting this pull request, the copyright holder is agreeing to the license the submitted work under the following licenses:
  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested

[WardBrian]

I think this is good to go

[jgabry]

Cool, thanks for the quick review