Bazel cmake rule overrides CMake build flag [CMAKE_CXX_COMPILER].

I am trying to build [OpenCV](https://github.com/opencv/opencv) on a Ubuntu 22.04 machine running Bazel 6.1.1. My workspace is setup as follows:

WORKSPACE:

```
http_archive(
name = "rules_foreign_cc",
sha256 = "476303bd0f1b04cc311fc258f1708a5f6ef82d3091e53fd1977fa20383425a6a",
strip_prefix = "rules_foreign_cc-0.10.1",
url = "https://github.com/bazelbuild/rules_foreign_cc/releases/download/0.10.1/rules_foreign_cc-0.10.1.tar.gz",)

load("@rules_foreign_cc//foreign_cc:repositories.bzl", "rules_foreign_cc_dependencies")

rules_foreign_cc_dependencies()

http_archive(
name = "opencv",
build_file = "//tools:opencv.BUILD",
sha256 = "62f650467a60a38794d681ae7e66e3e8cfba38f445e0bf87867e2f2cdc8be9d5",
strip_prefix = "opencv-4.8.1",
urls = ["https://github.com/opencv/opencv/archive/refs/tags/4.8.1.tar.gz"],
)
```

opencv.BUILD:

```
load("@rules_foreign_cc//foreign_cc:defs.bzl", "cmake")

filegroup(
name = "all_srcs",
srcs = glob(["**"]),
)

cmake(
name = "opencv",
build_args = [
"-j16",
],
cache_entries = {
"CMAKE_CXX_COMPILER": "g++",
"CMAKE_CXX_STANDARD": "17",
"BUILD_opencv_world": "ON",
"BUILD_SHARED_LIBS": "ON",
},
env = {
"CMAKE_BUILD_TYPE": "Release",
"CMAKE_BUILD_PARALLEL_LEVEL": "16",
},
linkopts = [
"-lstdc++",
],
lib_source = "all_srcs",
out_include_dir = "include/opencv4",
out_shared_libs = ["libopencv_world.so"],
visibility = ["//visibility:public"],
)
```

Trying to build the workspace CMake fails to build OpenCV and I see the following errors (and many more of the same kind):
```
/usr/bin/ld: /usr/include/c++/11/bits/basic_string.tcc:212: undefined reference to `std::__throw_logic_error(char const*)'

/usr/include/c++/11/ext/new_allocator.h:145: undefined reference to `operator delete(void*, unsigned long)'

/usr/include/c++/11/bits/basic_ios.h:462: undefined reference to `std::ios_base::ios_base()'
```

Checking Bazel's build log I noticed that in the CMake configuration both the C and the C++ compiler point to `/usr/bin/gcc` and I tried to change that by not relying on the default CMake configuration but by directly setting the C++ compiler to use `g++`. While setting the `CMAKE_CXX_STANDARD` changed the CMake output from `11` to `17` setting `CMAKE_CXX_COMPILER` does not change the CMake configuration at all.

I was able to reproduce this issue building OpenCV only using CMake without Bazel and setting the `CMAKE_CXX_COMPILER` to `gcc`.

Start by reproducing the failure with the WORKSPACE and opencv.BUILD examples, then compare the CMake configuration and Bazel build log to determine where CMAKE_CXX_COMPILER is overridden. Done means the requested C++ compiler is honored and the OpenCV build completes without the reported linker errors.

Written by the indexing model from the issue text.