cmd/cgo/internal/testcarchive: TestCompileWithoutShared failures

```
#!watchflakes
default <- pkg == "cmd/cgo/internal/testcarchive" && test == "TestCompileWithoutShared"
```

Issue created automatically to collect these failures.

Example ([log](https://ci.chromium.org/b/8733462684540614305)):

=== RUN TestCompileWithoutShared
carchive_test.go:1094: [go build -buildmode=c-archive -gcflags=-shared=false -o libgo2.a ./libgo2]
# testcarchive/libgo2
/Users/swarming/.swarming/wocebm_48/ir/x/w/goroot/pkg/tool/darwin_amd64/link: running /Users/swarming/.swarming/wocebm_48/ir/cache/tools/15e204a/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar failed: exit status 1
/Users/swarming/.swarming/wocebm_48/ir/cache/tools/15e204a/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: $WORK/b001/exe/a.out.a(000002.o) has no symbols
/Users/swarming/.swarming/wocebm_48/ir/cache/tools/15e204a/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: $WORK/b001/exe/a.out.a(000003.o) has no symbols
fatal error: /Users/swarming/.swarming/wocebm_48/ir/cache/tools/15e204a/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: can't write to output file (Device error)
/Users/swarming/.swarming/wocebm_48/ir/cache/tools/15e204a/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar: internal ranlib command failed

carchive_test.go:1096: exit status 1
--- FAIL: TestCompileWithoutShared (4.55s)

— [watchflakes](https://go.dev/wiki/Watchflakes)