Use native cmake unity support:

* Remove hand-rolled unity sources
* unity unavailable for cmake 3.15 and earlier
* remove deprecated target configure option

Builds/CMake/deps/Protobuf.cmake

@@ -42,6 +42,7 @@ if (local_protobuf OR NOT Protobuf_FOUND)
       -Dprotobuf_DEBUG_POSTFIX=_d
       -Dprotobuf_WITH_ZLIB=$<IF:$<BOOL:${has_zlib}>,ON,OFF>
       $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
+      $<$<BOOL:${unity}>:-DCMAKE_UNITY_BUILD=ON}>
       $<$<NOT:$<BOOL:${is_multiconfig}>>:-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}>
       $<$<BOOL:${MSVC}>:
 	"-DCMAKE_CXX_FLAGS=-GR -Gd -fp:precise -FS -EHa -MP"

Builds/CMake/deps/Rocksdb.cmake

@@ -76,6 +76,7 @@ if (local_rocksdb)
       -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
       -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
       $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
+      $<$<BOOL:${unity}>:-DCMAKE_UNITY_BUILD=ON}>
       -DCMAKE_DEBUG_POSTFIX=_d
       $<$<NOT:$<BOOL:${is_multiconfig}>>:-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}>
       -DBUILD_SHARED_LIBS=OFF

Builds/CMake/deps/Soci.cmake

@@ -58,6 +58,7 @@ else()
       $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
       $<$<BOOL:${CMAKE_TOOLCHAIN_FILE}>:-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}>
       $<$<BOOL:${VCPKG_TARGET_TRIPLET}>:-DVCPKG_TARGET_TRIPLET=${VCPKG_TARGET_TRIPLET}>
+      $<$<BOOL:${unity}>:-DCMAKE_UNITY_BUILD=ON}>
       -DCMAKE_PREFIX_PATH=${CMAKE_BINARY_DIR}/sqlite3
       -DCMAKE_MODULE_PATH=${CMAKE_CURRENT_SOURCE_DIR}/Builds/CMake
       -DCMAKE_INCLUDE_PATH=$<JOIN:$<TARGET_PROPERTY:sqlite,INTERFACE_INCLUDE_DIRECTORIES>,::>
@@ -74,6 +75,7 @@ else()
       # proper imported targets, this next line can be removed
       # (as well as the get_property above that sets _boost_incs)
       -DBoost_INCLUDE_DIRS=$<JOIN:${_boost_incs},::>
+      -DBoost_INCLUDE_DIR=$<JOIN:${_boost_incs},::>
       -DBOOST_ROOT=${BOOST_ROOT}
       -DWITH_BOOST=ON
       -DBoost_FOUND=ON

Builds/CMake/deps/gRPC.cmake

@@ -204,6 +204,7 @@ else ()
         $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:-DCMAKE_VERBOSE_MAKEFILE=ON>
         $<$<BOOL:${CMAKE_TOOLCHAIN_FILE}>:-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}>
         $<$<BOOL:${VCPKG_TARGET_TRIPLET}>:-DVCPKG_TARGET_TRIPLET=${VCPKG_TARGET_TRIPLET}>
+        $<$<BOOL:${unity}>:-DCMAKE_UNITY_BUILD=ON}>
         -DCMAKE_DEBUG_POSTFIX=_d
         $<$<NOT:$<BOOL:${is_multiconfig}>>:-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}>
         -DgRPC_BUILD_TESTS=OFF
@@ -347,7 +348,9 @@ target_link_libraries (grpc_pbufs protobuf::libprotobuf "gRPC::grpc++${grpc_suff
 target_compile_options (grpc_pbufs
   PRIVATE
     $<$<BOOL:${MSVC}>:-wd4065>
+    $<$<NOT:$<BOOL:${MSVC}>>:-Wno-deprecated-declarations>
   PUBLIC
+    $<$<BOOL:${MSVC}>:-wd4996>
     $<$<BOOL:${is_xcode}>:
       --system-header-prefix="google/protobuf"
       -Wno-deprecated-dynamic-exception-spec