Add Linux build support (development)

[pskeshu]

Motivation

I came across ScopeOne, and out of curiosity tried building it on Linux. Beyond
the curiosity, cross-platform builds make a project meaningfully easier to
develop on and contribute to — even if production stays on Windows. The
encouraging part is that the hard work is already done: the multi-process core is
built on Qt's cross-platform primitives (QProcess, QSharedMemory,
QLocalServer), so very little of the runtime is actually Windows-specific. The
gap was mostly the build system plus a couple of small spots.

This PR makes ScopeOne build and run on Linux with the demo camera, while
leaving the Windows build path untouched.

What's in this PR (4 files, +74/−39)

Everything platform-specific is guarded behind if(WIN32)/else() so the Windows
build is unchanged:

• ScopeOneCore/CMakeLists.txt — Linux branch resolves deps via
  find_package (system Qt6, OpenCV [core+imgproc only, to avoid the
  viz→VTK chain], TIFF, ZLIB) and links MMCore as an imported static library
  built from mmCoreAndDevices.
• CMakeLists.txt — guard the hardcoded C:/Qt/... prefix so it's
  Windows-only.
• ScopeOneCore/src/RecordingManager.cpp — give SaveBackend::TiffOptions
  an explicit constructor instead of default member initializers; GCC rejects
  = {} as a default argument for the nested aggregate (MSVC accepts it).
  Behavior unchanged.
• src/ScopeOneLocalApiServer.cpp — guard the Win32
  CreateFileMapping/MapViewOfFile frame export behind #if defined(_WIN32).
  The local API socket server still runs on Linux; only the zero-copy shared-frame
  export is disabled for now (see follow-ups).

Building the Micro-Manager dependency

I built only the minimal pieces from mmCoreAndDevices (no vendor adapters) via
the standard autotools path:

# in a micro-manager checkout (mmCoreAndDevices as submodule)
./autogen.sh && ./configure --without-java
make -C mmCoreAndDevices/MMDevice
make -C mmCoreAndDevices/MMCore
make -C mmCoreAndDevices/DeviceAdapters/DemoCamera

This yields libMMCore.a, libMMDevice.a, and libmmgr_dal_DemoCamera.so.0
(no boost or swig required). Then the usual ScopeOne build, pointing the core
CMake at that checkout via external/mmCoreAndDevices.

Verification

• Headless smoke test: MMCore loads config/MMConfig_demo.cfg and snapImage()
  returns a 512×512 16-bit frame.
• GUI launches cleanly.
• Tested on Manjaro Linux, Qt 6.11.1, OpenCV 4.13, GCC 16, CMake 4.x.
• I have not been able to test the Windows build; the changes are guarded to
  preserve it, but someone with a Windows setup should confirm.

Scope / non-goals

• Demo camera only — real device adapters remain Windows-bound by vendor SDKs, as
  expected for Micro-Manager.
• Dev/CI focus, not production parity.

Known follow-ups (happy to do these if useful)

1. Multi-camera / agent path — AgentProtocol.h hardcodes
   ScopeOne_Agent.exe; needs a platform-aware name on Linux. The single-camera
   demo uses the native path and is unaffected.
2. Local-API frame export — port the guarded-out Win32 shared memory to POSIX
   shm_open/mmap (or QSharedMemory) so external clients get zero-copy frames
   on Linux too.
3. Adapter staging — stage the device-adapter .so next to the binary in
   CMake instead of copying it manually.

Questions for maintainers

• Would you welcome Linux dev support upstream, or is Windows-only intentional for
  now?
• How would you prefer the mmCoreAndDevices dependency wired on Linux
  (find-or-fetch in CMake, documented manual build, submodule)? I followed the
  existing external/ layout but kept it flexible.

Thanks for open-sourcing this — it's a clean codebase to work in.