[libc] Add proxy headers for fenv.h types.

[lntue]

Context: #87017 #87598

This is the continuation of #87863.

Add a proxy header for fenv.h types so that our implementations and tests will work nicely for both overlay and full build modes.

• Add libc/hdr/fenv_t.h and libc\hdr\fexcept_t that will include the system <fenv.h> in overlay mode or include the corresponding header in libc/include/llvm-libc-types/ in full build mode.
• Add its corresponding cmake targets in libc/hdr/CMakeLists.txt.
• Replacing the remaining #include <fenv.h> and cmake target dependency on libc.include.fenv.
• Add their corresponding bazel targets in utils/bazel/llvm-project-overlay/libc/BUILD.bazel.
• Update bazel dependencies.

[llvmbot]

@llvm/issue-subscribers-libc

Author: None (lntue)

Context: https://github.com//pull/87017 https://github.com//pull/87598

This is the continuation of #87863.

Add a proxy header for fenv.h types so that our implementations and tests will work nicely for both overlay and full build modes.

• Add libc/hdr/fenv_t.h and libc\hdr\fexcept_t that will include the system <fenv.h> in overlay mode or include the corresponding header in libc/include/llvm-libc-types/ in full build mode.
• Add its corresponding cmake targets in libc/hdr/CMakeLists.txt.
• Replacing the remaining #include <fenv.h> and cmake target dependency on libc.include.fenv.
• Add their corresponding bazel targets in utils/bazel/llvm-project-overlay/libc/BUILD.bazel.
• Update bazel dependencies.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: None (lntue)

Context: https://github.com//pull/87017 https://github.com//pull/87598

This is the continuation of #87863.

Add a proxy header for fenv.h types so that our implementations and tests will work nicely for both overlay and full build modes.

• Add libc/hdr/fenv_t.h and libc\hdr\fexcept_t that will include the system <fenv.h> in overlay mode or include the corresponding header in libc/include/llvm-libc-types/ in full build mode.
• Add its corresponding cmake targets in libc/hdr/CMakeLists.txt.
• Replacing the remaining #include <fenv.h> and cmake target dependency on libc.include.fenv.
• Add their corresponding bazel targets in utils/bazel/llvm-project-overlay/libc/BUILD.bazel.
• Update bazel dependencies.

Can you please assign it to me.