Replace GMP on MSVC builds with Chia's MPIR.

CMakeLists.txt

@@ -252,7 +252,7 @@ if("$ENV{CFLAGS}" STREQUAL "")
 		endif()
 	else()
 		if (MSVC)
-			set(COMP_FLAGS "/O2" CACHE STRING "Default compiler flags.")
+			set(COMP_FLAGS "/MP /O2" CACHE STRING "Default compiler flags.")
 		else()
 			set(COMP_FLAGS "-pipe -std=c99 -O2 -funroll-loops -fomit-frame-pointer" CACHE STRING "Default compiler flags.")
 		endif()
@@ -311,7 +311,8 @@ else()
 	set(PFLAGS "")
 endif()
 
-if(ARITH STREQUAL "gmp" OR ARITH STREQUAL "gmp-sec")
+# We'll be using our custom MPIR build instead of GMP for MSVC builds
+if((ARITH STREQUAL "gmp" OR ARITH STREQUAL "gmp-sec") AND (NOT MSVC))
 	include(cmake/gmp.cmake)
 	if(GMP_FOUND)
 		include_directories(${GMP_INCLUDE_DIR})

src/CMakeLists.txt

@@ -231,7 +231,13 @@ if (STLIB)
 		add_library(${RELIC_S} STATIC ${RELIC_SRCS} ${ARITH_OBJS})
 	endif()
 	add_dependencies(${RELIC_S} arith_objs)
-	target_link_libraries(${RELIC_S} ${ARITH_LIBS})
+	if(MSVC)
+		message(STATUS "Configured with MPIR (GMP fork)")
+		target_include_directories(${RELIC_S} PUBLIC ${MPIR_INCLUDE_DIR})
+		target_link_libraries(${RELIC_S} PRIVATE ${MPIR_IMPLIB})
+	else()
+		target_link_libraries(${RELIC_S} ${ARITH_LIBS})
+	endif()
 	link_libs(${RELIC_S})
 	install(TARGETS ${RELIC_S} ARCHIVE DESTINATION lib)
 endif(STLIB)