[cmake] Turn everything with incompatible licenses off by default:

The default should be a ROOT binary that respects its license; any
build that creates GPLed binaries should be an active decision.

Affected are uses of fftw3, gsl, Pythia 8, and unuran (all GPL), as well as Pythia 6 which does not seem to have a license.

cmake/modules/RootBuildOptions.cmake

@@ -128,7 +128,7 @@ ROOT_BUILD_OPTION(davix ON "Enable support for Davix (HTTP/WebDAV access)")
 ROOT_BUILD_OPTION(dcache OFF "Enable support for dCache (requires libdcap from DESY)")
 ROOT_BUILD_OPTION(dev OFF "Enable recommended developer compilation flags, reduce exposed includes")
 ROOT_BUILD_OPTION(exceptions ON "Enable compiler exception handling")
-ROOT_BUILD_OPTION(fftw3 ON "Enable support for FFTW3")
+ROOT_BUILD_OPTION(fftw3 OFF "Enable support for FFTW3 [GPL]")
 ROOT_BUILD_OPTION(fitsio ON "Enable support for reading FITS images")
 ROOT_BUILD_OPTION(fortran OFF "Build Fortran components of ROOT")
 ROOT_BUILD_OPTION(gdml ON "Enable support for GDML (Geometry Description Markup Language)")
@@ -142,7 +142,7 @@ ROOT_BUILD_OPTION(imt ON "Enable support for implicit multi-threading via Intel
 ROOT_BUILD_OPTION(jemalloc OFF "Use jemalloc memory allocator, deprecated")
 ROOT_BUILD_OPTION(libcxx OFF "Build using libc++")
 ROOT_BUILD_OPTION(macos_native OFF "Disable looking for libraries, includes and binaries in locations other than a native installation (MacOS only)")
-ROOT_BUILD_OPTION(mathmore ON "Build libMathMore extended math library (requires GSL)")
+ROOT_BUILD_OPTION(mathmore OFF "Build libMathMore extended math library (requires GSL) [GPL]")
 ROOT_BUILD_OPTION(memory_termination OFF "Free internal ROOT memory before process termination (experimental, used for leak checking)")
 ROOT_BUILD_OPTION(mlp ON "Enable support for TMultilayerPerceptron classes' federation")
 ROOT_BUILD_OPTION(minuit2 ON "Build Minuit2 minimization library")
@@ -160,8 +160,8 @@ ROOT_BUILD_OPTION(pyroot ON "Enable support for automatic Python bindings (PyROO
 ROOT_BUILD_OPTION(pyroot-python2 OFF "Enable Python 2 support in PyROOT")
 ROOT_BUILD_OPTION(pyroot_legacy OFF "Use legacy Python bindings for ROOT, deprecated")
 ROOT_BUILD_OPTION(pythia6_nolink OFF "Delayed linking of Pythia6 library")
-ROOT_BUILD_OPTION(pythia6 ON "Enable support for Pythia 6.x")
-ROOT_BUILD_OPTION(pythia8 ON "Enable support for Pythia 8.x")
+ROOT_BUILD_OPTION(pythia6 OFF "Enable support for Pythia 6.x [unlicensed]")
+ROOT_BUILD_OPTION(pythia8 OFF "Enable support for Pythia 8.x [GPL]")
 ROOT_BUILD_OPTION(qt5web OFF "Enable support for Qt5 web-based display (requires Qt5::WebEngine and Qt5::WebEngineWidgets)")
 ROOT_BUILD_OPTION(qt6web OFF "Enable support for Qt6 web-based display (requires Qt6::WebEngineCore and Qt6::WebEngineWidgets)")
 ROOT_BUILD_OPTION(r OFF "Enable support for R bindings (requires R, Rcpp, and RInside)")
@@ -184,7 +184,7 @@ ROOT_BUILD_OPTION(tmva-sofie OFF "Build TMVA with support for sofie - fast infer
 ROOT_BUILD_OPTION(tmva-pymva ON "Enable support for Python in TMVA (requires numpy)")
 ROOT_BUILD_OPTION(tmva-rmva OFF "Enable support for R in TMVA")
 ROOT_BUILD_OPTION(spectrum ON "Enable support for TSpectrum")
-ROOT_BUILD_OPTION(unuran OFF "Enable support for UNURAN (package for generating non-uniform random numbers)")
+ROOT_BUILD_OPTION(unuran OFF "Enable support for UNURAN (package for generating non-uniform random numbers) [GPL]")
 ROOT_BUILD_OPTION(uring OFF "Enable support for io_uring (requires liburing and Linux kernel >= 5.1)")
 ROOT_BUILD_OPTION(vc OFF "Enable support for Vc (SIMD Vector Classes for C++)")
 ROOT_BUILD_OPTION(vdt ON "Enable support for VDT (fast and vectorisable mathematical functions)")
@@ -285,20 +285,20 @@ if(all)
  set(xproofd_defvalue OFF)
 endif()
 
-#--- The 'builtin_all' option swithes ON old the built in options-------------------------------
+#--- The 'builtin_all' option switches ON all the built in options but GPL-------------------------------
 if(builtin_all)
   set(builtin_afterimage_defvalue ON)
   set(builtin_cfitsio_defvalue ON)
   set(builtin_clang_defvalue ON)
   set(builtin_cling_defvalue ON)
   set(builtin_cppzmq_defvalue ON)
   set(builtin_davix_defvalue ON)
-  set(builtin_fftw3_defvalue ON)
+#  set(builtin_fftw3_defvalue ON) (GPL)
   set(builtin_freetype_defvalue ON)
   set(builtin_ftgl_defvalue ON)
   set(builtin_gl2ps_defvalue ON)
   set(builtin_glew_defvalue ON)
-  set(builtin_gsl_defvalue ON)
+#  set(builtin_gsl_defvalue ON) (GPL)
   set(builtin_gtest_defvalue ON)
   set(builtin_llvm_defvalue ON)
   set(builtin_lz4_defvalue ON)
@@ -308,7 +308,7 @@ if(builtin_all)
   set(builtin_openui5_defvalue ON)
   set(builtin_pcre_defvalue ON)
   set(builtin_tbb_defvalue ON)
-  set(builtin_unuran_defvalue ON)
+#  set(builtin_unuran_defvalue ON) (GPL)
   set(builtin_vc_defvalue ON)
   set(builtin_vdt_defvalue ON)
   set(builtin_veccore_defvalue ON)