Fix Clp library detection for vcpkg on Windows #28423
## Problem
Building OpenCV with `WITH_CLP=ON` on Windows (vcpkg) fails:
LINK : fatal error LNK1181: cannot open input file 'libClp.lib'
vcpkg generates `Clp.lib` and `CoinUtils.lib`, but OpenCV expected `libClp.lib`/`libCoinUtils.lib`.
## Solution
Modernize CLP detection with a robust, platform-aware approach:
1. **CMake `find_package(Clp CONFIG)`**: detects vcpkg and uses imported targets (`Coin::Clp`, `Coin::CoinUtils`)
2. **Fallback**: pkg-config on Unix/Linux
3. **Skip** Android/iOS
## Benefits
✅ Fixes Windows build with vcpkg
✅ Uses modern CMake targets
✅ Backward compatible with Unix/Linux
✅ Safe for CI and mobile builds
✅ Graceful fallback if CLP unavailable
## Testing
- **Windows 11 + vcpkg**: build succeeds
- **No CLP installed**: configure/build succeeds
- **Linux/Unix**: existing workflows unaffected
- **Android/iOS**: properly skipped
## Changes
- Update `cmake/OpenCVFindLibsPerf.cmake`
- Replace hardcoded library names with CMake targets
- Add mobile platform guards
- Preserve backward compatibility
Fixes#26592
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### Pull Request Readiness Checklist
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch (`4.x`)
- [x] There is a reference to the original bug report and related work (#26592)
- [x] The feature is well documented and sample code can be built with the project CMake
- [x] No additional tests required - this is a build system fix that maintains existing functionality
Chevi koren
1f8257adad