Wrong cc toolchain selected on Mac

[katre]

@jayconrod reports: When testing with this flag on in rules_go at dd527c7d with Bazel 0.26.0rc8 on macOS, I'm seeing this error:

$ bazel build --incompatible_enable_cc_toolchain_resolution tests/legacy/examples/cgo:sub
> > Loading: 
Loading: 0 packages loaded
Analyzing: target //tests/legacy/examples/cgo:sub (0 packages loaded, 0 targets configured)
INFO: Analyzed target //tests/legacy/examples/cgo:sub (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
bazel: Entering directory `/private/var/tmp/_bazel_jayconrod/95575c789b578fe26b1744a32454af42/execroot/io_bazel_rules_go/'
[0 / 2] [Prepa] BazelWorkspaceStatusAction stable-status.txt
ERROR: /Users/jayconrod/go/src/github.com/bazelbuild/rules_go/tests/legacy/examples/cgo/BUILD.bazel:29:1: GoCompilePkg tests/legacy/examples/cgo/darwin_amd64_stripped/sub%/github.com/bazelbuild/rules_go/examples/cgo/sub.a failed (Exit 1) builder failed: error executing command bazel-out/host/bin/external/go_sdk/builder compilepkg -sdk external/go_sdk -installsuffix darwin_amd64 -src tests/legacy/examples/cgo/sub/floor.go -importpath ... (remaining 19 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
ld: framework not found UIKit
clang: error: linker command failed with exit code 1 (use -v to see invocation)
compilepkg: error running subcommand: exit status 1
bazel: Leaving directory `/private/var/tmp/_bazel_jayconrod/95575c789b578fe26b1744a32454af42/execroot/io_bazel_rules_go/'
Target //tests/legacy/examples/cgo:sub failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.488s, Critical Path: 0.29s
INFO: 0 processes.
FAILED: Build did NOT complete successfully
FAILED: Build did NOT complete successfully

It looks like -framework UIKit is being added to the C++ link flags. This target doesn't set link flags on its own, so I think this is coming from cc_common. Is that expected?

Originally posted by @jayconrod in #7260 (comment)

[katre]

The cause is the incomplete TODO here: https://source.bazel.build/bazel/+/8bd7e4822ed96615ccac77cc40ca96eddc74c510:tools/osx/crosstool/BUILD.tpl;l=89