Use installed protobuf on Linux

external/cld3/CMakeLists.txt

@@ -16,7 +16,7 @@ set(cld3_src ${cld3_loc}/src)
 set(gen_loc ${cld3_loc}/build/gen)
 set(gen_dst ${gen_loc}/cld_3/protos)
 
-if (DESKTOP_APP_USE_PACKAGED)
+if (DESKTOP_APP_USE_PACKAGED OR LINUX)
     find_package(Protobuf)
     if (NOT Protobuf_FOUND)
         find_package(protobuf REQUIRED CONFIG)
@@ -30,9 +30,6 @@ elseif (WIN32)
 else()
     set(protoc_executable ${libs_loc}/protobuf/build/protoc)
     set(protobuf_lib ${libs_loc}/protobuf/build/libprotobuf-lite.a)
-    if (LINUX)
-        target_compile_options(external_cld3_bundled PRIVATE -Wno-implicit-fallthrough)
-    endif()
 endif()
 if (PROTOBUF_PROTOC_EXECUTABLE)
     set(protoc_executable ${PROTOBUF_PROTOC_EXECUTABLE})
@@ -87,13 +84,18 @@ PRIVATE
     script_span/fixunicodevalue.cc
 )
 
+target_compile_options_if_exists(external_cld3_bundled
+PRIVATE
+    -Wno-implicit-fallthrough
+)
+
 target_include_directories(external_cld3_bundled
 PUBLIC
     ${cld3_src}
     ${gen_loc}
 )
 
-if (NOT DESKTOP_APP_USE_PACKAGED)
+if (NOT DESKTOP_APP_USE_PACKAGED AND NOT LINUX)
     target_include_directories(external_cld3_bundled
     PUBLIC
         ${libs_loc}/protobuf/src