initial version of SQIsign

Co-authored-by: Jorge Chavez-Saab <jorgechavezsaab@gmail.com>
Co-authored-by: Maria Corte-Real Santos <36373796+mariascrs@users.noreply.github.com>
Co-authored-by: Luca De Feo <github@defeo.lu>
Co-authored-by: Jonathan Komada Eriksen <jonathan.eriksen97@gmail.com>
Co-authored-by: Basil Hess <bhe@zurich.ibm.com>
Co-authored-by: Antonin Leroux <18654258+tonioecto@users.noreply.github.com>
Co-authored-by: Patrick Longa <plonga@microsoft.com>
Co-authored-by: Lorenz Panny <lorenz@yx7.cc>
Co-authored-by: Francisco Rodríguez-Henríquez <francisco.rodriguez@tii.ae>
Co-authored-by: Sina Schaeffler <108983332+syndrakon@users.noreply.github.com>
Co-authored-by: Benjamin Wesolowski <19474926+Calodeon@users.noreply.github.com>

.cmake/gmpconfig.cmake

@@ -0,0 +1,36 @@
+
+if (ENABLE_GMP_BUILD)
+  # Download and build own libgmp version
+  if (POLICY CMP0135)
+    cmake_policy(SET CMP0135 NEW)
+  endif()
+  SET(GMP_BUILD_CONFIG_ARGS "" CACHE STRING "Some user-specified gmp config options")
+  option(ENABLE_GMP_STATIC "Option to statically link. Default is dynamic linking" OFF)
+
+  if (ENABLE_GMP_STATIC)
+    set(GMP_LIB_SUFFIX ${CMAKE_SHARED_LIBRARY_SUFFIX})
+  else()
+    set(GMP_LIB_SUFFIX ${CMAKE_STATIC_LIBRARY_SUFFIX})
+  endif()
+
+  message("${GMP_BUILD_CONFIG_ARGS}")
+  include(ExternalProject)
+  find_program(MAKE_EXE NAMES make gmake nmake)
+  set(libgmp_INSTALL_DIR "${CMAKE_BINARY_DIR}/libgmp")
+  ExternalProject_Add(libgmp_external
+    PREFIX ${libgmp_INSTALL_DIR}
+    URL               https://gmplib.org/download/gmp/gmp-6.2.1.tar.xz
+    URL_HASH          SHA256=fd4829912cddd12f84181c3451cc752be224643e87fac497b69edddadc49b4f2
+    CONFIGURE_COMMAND ${libgmp_INSTALL_DIR}/src/libgmp_external/configure --prefix=${libgmp_INSTALL_DIR} ${GMP_BUILD_CONFIG_ARGS}
+    BUILD_COMMAND     ${MAKE_EXE} -j8
+    INSTALL_COMMAND   ${MAKE_EXE} install
+  )
+
+  set(GMP ${libgmp_INSTALL_DIR}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}gmp${GMP_LIB_SUFFIX})
+  include_directories(${libgmp_INSTALL_DIR}/include)
+else()
+  # use system gmp version
+  find_library(GMP gmp)
+  find_path(GMP_INCLUDE gmp.h)
+  include_directories(${GMP_INCLUDE})
+endif()