Seen with curl-for-win linux-musl-from-mac build with gcc 9.2.0.
```
n file included from /Users/runner/work/curl-for-win/curl-for-win/curl/_x64-linux-musl-bld/src/CMakeFiles/curl.dir/Unity/unity_0_c.c:136:
/Users/runner/work/curl-for-win/curl-for-win/curl/_x64-linux-musl-bld/src/tool_ca_embed.c:4:28: warning: redundant redeclaration of 'curl_ca_embed' [-Wredundant-decls]
4 | extern const unsigned char curl_ca_embed[];
| ^~~~~~~~~~~~~
In file included from /Users/runner/work/curl-for-win/curl-for-win/curl/_x64-linux-musl-bld/src/CMakeFiles/curl.dir/Unity/unity_0_c.c:88:
/Users/runner/work/curl-for-win/curl-for-win/curl/src/tool_operate.c:107:28: note: previous declaration of 'curl_ca_embed' was here
107 | extern const unsigned char curl_ca_embed[];
| ^~~~~~~~~~~~~
```
https://github.com/curl/curl-for-win/actions/runs/11192203640/job/31116070669#step:3:4894
Follow-up to 8a3740bc8e#14059Closes#15307
Add the ability to embed a CA bundle into the curl binary. It is used
when no other runtime or build-time option set one.
This helps curl-for-win macOS and Linux builds to run standalone, and
also helps Windows builds to avoid picking up the CA bundle from an
arbitrary (possibly world-writable) location (though this behaviour is
not currently disablable).
Usage:
- cmake: `-DCURL_CA_EMBED=/path/to/curl-ca-bundle.crt`
- autotools: `--with-ca-embed=/path/to/curl-ca-bundle.crt`
- Makefile.mk: `CURL_CA_EMBED=/path/to/curl-ca-bundle.crt`
Also add new command-line option `--dump-ca-embed` to dump the embedded
CA bundle to standard output.
Closes#14059
