build(deb): fix source tree path leaking into package

[einhander]

 - Add -fdebug-prefix-map to debian/rules to remap absolute build
    paths to relative in DWARF debug info
  - Fix configure_file to output Version.cpp into BINARY_DIR instead
    of polluting the source tree
  - Replace global include_directories with target_include_directories
    to scope include paths to the target only
  - Fix Makefile install target: pass DESTDIR as env variable and
    --prefix separately so cmake --install uses correct paths
  - Add override_dh_auto_install with PREFIX=/usr in debian/rules
  - Add CMAKE_*_RPATH options to control rpath behaviour
  - Switch deb target from dpkg-buildpackage -F to debuild -uc -us

[reybits]

Thanks for the cleanup - the debug-path remap, scoped target includes, and proper DESTDIR/--prefix split for cmake --install are all good improvements. Two issues need be addressed before this can merge, both around the include/sources changes in CMakeLists.txt:

1. target_include_directories is missing BEFORE - macOS fmt regression

Earlier in the file, directory-scope include_directories(${GLFW3_INCLUDE_DIRS}) (line 117) adds /opt/homebrew/include on macOS. With the old include_directories(BEFORE...) the bundled third-party/fmtlib/include was guaranteed to come first. The new target_include_directories(...PRIVATE...) appends, so on a Homebrew system #include <fmt/format.h> resolves to the system fmt (v12) instead of the bundled one (v10), reintroducing the ABI conflict that the BEFORE keyword was originally added to fix.

  target_include_directories(${APPLICATION_NAME} BEFORE PRIVATE
      ${CMAKE_CURRENT_SOURCE_DIR}/src
      ${CMAKE_CURRENT_SOURCE_DIR}/third-party/fmtlib/include
      ${CMAKE_CURRENT_SOURCE_DIR}/third-party/glad/include
      ${CMAKE_CURRENT_BINARY_DIR}/src
      )

2. Stale src/Version.cpp from prior builds → duplicate-symbol link error

src/Version.cpp is .gitignored, not deleted. Anyone who built before this PR (and CI caches) still has it on disk. file(GLOB_RECURSE SVIEW_SOURCES "src/*.cpp") picks up the stale source-tree copy and the explicit list(APPEND... ${CMAKE_CURRENT_BINARY_DIR}/src/Version.cpp), so the build fails at link time with multiple definition of 'version::getMajor()' (and friends).

Either remove the stale file at configure time:

  file(REMOVE "${CMAKE_CURRENT_SOURCE_DIR}/src/Version.cpp")
  file(GLOB_RECURSE SVIEW_SOURCES "src/*.cpp")
  list(APPEND SVIEW_SOURCES "${CMAKE_CURRENT_BINARY_DIR}/src/Version.cpp")

or exclude it from the glob with list(FILTER SVIEW_SOURCES EXCLUDE REGEX "src/Version\\.cpp$").

Optional nits (non-blocking)

• CMAKE_SKIP_BUILD_RPATH=FALSE and CMAKE_BUILD_WITH_INSTALL_RPATH=FALSE in dist/debian/rules are CMake defaults - they can be dropped to keep the diff focused on what actually changes.
• CMAKE_INSTALL_RPATH_USE_LINK_PATH=TRUE will embed the linker search paths into the binary's RUNPATH; expect lintian to flag binary-or-shlib-defines-rpath. Worth confirming it's actually needed.
• override_dh_auto_install: dh_auto_install -- PREFIX=/usr - cmake --install doesn't honor a PREFIX variable, and debhelper's cmake buildsystem already sets CMAKE_INSTALL_PREFIX=/usr. The override is a no-op; either drop it or add -DCMAKE_INSTALL_PREFIX=/usr to override_dh_auto_configure if the intent was different.
• Switching from dpkg-buildpackage -F -tc to debuild -uc -us loses the -tc "clean after build" behavior; not critical, just worth noting.

Happy to merge once (1) and (2) are addressed.